US3560157A - Surface analyses - Google Patents

Abstract

A PROCESS FOR CONTROLLING OR MONITORING OPERATIONS IN WHICH THE PRODUCTION OF CHEMICALLY REACTIVE MATERIALS IS STUDIED BY SELECTING REPRESENTATIVE ARTICLES HAVING SURFACES MODIFIED BY CHEMICALLY REACTIVE MATERIAL AND CONTACTING THOSE SURFACES WITH A RADIOACTIVE CHEMICAL THAT HAS AT LEAST ONE COMPONENT THAT IS SELECTIVELY RETAINED BY AT LEAST A PART OF THE MATERIAL. THE CHEMICAL IS SUCH THAT IT WILL LEAVE THE MATERIAL AT AN EVAPORATIVE RATE WHICH IS MEASURED, AND THE AMOUNT OF THE RETENTION OF THE CHEMICAL IS FOLLOWED BY MEASURING THE EVAPORATIVE RATE OF THE CHEMICAL. KNOWING THROUGH PREVIOUS DETERMINATIONS PRECISELY WHAT EVAPORATIVE RATES ATTAIN FROM PREVIOUSLY PREPARED SURFACES HAVING OR BEING THE DESIRED AND PROPER MATERIAL, ONE THUS CONTROLS THE CHEMICAL REACTIONS INVILVED TO AVOID THE ISSUANCE OF ARTICLES BEARING FAULTY MATERIAL.

Description

United States Patent Int. Cl. GOln 31/06; G21h /00 US. Cl. 23-230 8 Claims ABSTRACT OF THE DISCLOSURE A process for controlling or monitoring operations in which the production of chemically reactive materials is studied by selecting representative articles having surfaces modified by chemically reactive material and contacting those surfaces with a radioactive chemical that has at least one component that is selectively retained by at least a part of the material. The chemical is such that it will leave the material at an evaporative rate which is measured, and the amount of the retention of the chemical is followed by measuring the evaporative rate of the chemical. Knowing through previous determinations precisely what evaporative rates attain from previously'prepared surfaces having or being the desired and proper material, one thus controls the chemical reactions involved to avoid the issuance of articles bearing faulty material.

DISCLOSURE The invention relates to detection processes for studying surfaces on which materials have been deposited.

Disclosed and claimed herein is the detection of surface conditions which result upon the deposition of or alteration of surfaces to produce finished articles bearing the deposition or having the desired altered surface.

This case is a continuation-in-part of my application S.N. 506,566, filed on Nov. 5, 1965, and now US. Pat. No. 3,412,247, issued Nov. 9, 1968, which is a continuation-in-part of my application S.N. 161,246, filed on Dec. 21, 1961, now US. Pat. No. 3,297,874, issued Jan. 10, 1967, as a continuation-in-part of my application S.N. 78,284 filed on Dec. 27, 1960, now abandoned.

In those applications there is disclosed the rapid quantitative detection of nonvolatile contaminants using radiochemicals, and apparatus and compositions for effecting the detection are described. The disclosures of these applications are incorporated in this by reference thereto. In particular, a process is described for applying a volatile radioactive labeled material to the surface to be examnied, effecting partial evaporation under controlled conditions and measuring residual radioactivity due to the retention of radiochemical caused by the surface conditions such as the presence of contamination, thus effecting a measurement of the surface defect such as contamination. In the present application, one is concerned specifically with the study of a particular surface which has been deliberate- 1y prepared to produce desired effects in a saleable product. For example, the producer of yarns, filaments, and the like deserves to know whether his production line is producing fibers on which finish is properly deposited sa to amount, penetration and the like. In another instance the producer of paper needs similar information as to fillers or agents used in improving wet-strength. Similarly, a producer of metal in sheet form deserves accurate knowledge as to the deposition of rust preventatives or the like. There is provided by this invention processes for effecting an accurate analysis of the surface conditions produced by surface modifications effected in the manufacture of a given item.

The invention will be further understood by reference to the examples and disclosure given below. Examples I to VII correspond to Examples XII to XVII of S.N.

' 506,566 and the apparatus used in the examples below corresponds to that described in said application.

EXAMPLE I Fifty parts of a solution containing 0.1 microcurie of carbon 14 labeled tetrabromoethane (specific activity millicuries per millimole) dissolved in 150,000 parts of trifluorotrichloroethane, removed from a sealed ampule of 3 mm. outside diameter and drawn to a standard capillary on each end, was added to a 1 inch length of a 55 denier acetate rayon yarn containing a standard finish which length was positioned on a stainless steel surface. The addition was such that the fiber surfaces were substantially wetted by the liquid. Immediately after the application of the radiochemical solution, a thin end window Geiger Mueller detector, protected with a .15 mil Mylar shield, was positioned directly above the wet fibers and a constant flow of clean dry nitrogen passed over the sample and below the surface of the tube protection shield. Following evaporation of the solvent, the rate of evaporation of the radioactive labeled material was observed by plotting the counts per minute versus time and the areas under the evaporation curve measured by taking the total digital information obtained from the Geiger tube, analysing the data and expressing on a timed basis four sequential areas under the evaporation curve, as explained before. These areas provided the following numbers: 68, 57, 50, 46.

A similar determination made on identical fibers in the absence of finish provided similar number values of 15, 12, 9, 7. The higher numbers are a measure of the amount of finish.

When varying amounts of finish were applied to similar rayon fibers, the numbers obtained were always in a ratio relative to the amount of finish applied. Thus, this procedure can be used as an accurate measure of the amount of finish on fibers.

In a similar experiment the volatile solvent used was cyclopentane and the radiochemical was tridecane-C-14 with a specific activity of at least 40 millicuries per millimole. Similar, but not identical numerical results were obtained.

In another similar experiment, the radiochemical test solution used consisted essentially of the dimethyl ether of triethylene glycol C-14 dissolved in the volatile solvent diethyl ether. Similar but not identical results were again obtained. These experiments show that the amount of surface residue on the rayon fibers may be detected by this technique with different radiochemicals.

EXAMPLE II Using the precision volumetric dispenser described in S.N. 506,566 a 20-lambda volume of radiochemical test solution containing one part of tetrabromoethane- C14 dissolved in 60,000 parts of trifluorotrichloroethane was added dropwise to a fiat, horizontal and clean silicon surface. Following the positioning of a suitable detector above and impingement of dry gas nitrogen onto the surface, the desorption rate from the surface was observed. Expressing the areas under the evaporation curve as a direct function of the digital information, and permitting the prior evaporation of solvent, only background radiation could be detected in four sequential periods. When the same surface was contaminated with 20 micrograms of oil and similarly examined, the nu- 3 merical expressions were 35, 28, 24, and 22, thus detecting and measuring the contamination.

EXAMPLE III In an experiment similar to Example I, 1 inch of nylon monofilament having a standard processing finish on its surface was cut into one-eighth inch lengths and the eight pieces were positioned on a sample plate of glass which contained a standard concavity 5 mm. in depth and mm. in diameter for each filament. Then 0.5 ml. of ethyl ether was added to the fiber located in the concavity and the short lengths of fiber were removed with a scrupulously clean pair of forcepts. Following evaporation of the ethyl ether, lambda of a solution containing 0.5 microgram of tetrabromoethane-C14 in methylene chloride was added dropwise to the residue. Following evaporation of the solvent methylene chloride, the evaporative rate of the radioactive material was determined by passing a controlled flow of pure nitrogen gas at a rate of 1200 ml. per minute over the surface and between the surface and a thin end window G.M. tube. The various discharges in the GM. tube were analyzed by the equipment shown before and the counts per minute plotted against time on a strip chart recorder. The rate of evaporation of the radioactive material thus obtained was significantly lower than the rate observed when the same experiment was carried out on nylon monofilament which had been previously scrupulously cleaned of finish.

EXAMPLE IV One cubic centimeter of ether containing 10 parts per million of nonvolatile residue was evaporated into a glass planchlet similar to that used in Example III, and the nonvolatile residue on the planchlet was permitted to resume ambient temperature. Then 8 lambda of a solution containing tetra'bomoethane-C-14 dissolved in trifluorotrichloroethane was added to the planchlet and the volatile solvent evaporated. Subsequent measurement of the rate of evaporation of the radioactive tetrabromoethaneC-14 from the surface showed the precense of the nonvolatile residue previously deposited from the ethyl ether. When the identical experiment was carried out using ethyl ether of scrupulous purity, the observed rate of evaporation was much faster and in fact under the conditaions of the experiment, background levels were reached in a few seconds whereas background levels were reached only after several minutes in the case of the deposited residue.

EXAMPLE V In an experiment similar to Example IV, the amount of nonvolatile residue in a series of samples of trichloroethylene which had been obtained from washing the internal surfaces of piping used in pumping hydraulic oils showed that the rate of evaporation increased with the residues laid down from samples taken sequentially. This showed that the first samples contained higher amounts of residual oil and later samples lower amounts. By using this technique the efliciency of the cleaning steps and materials can be rapidly determined.

EXAMPLE VI Fifty parts of a solution containing tridecane-C-14 of specific activity 40 millicuries per millirnole in 100,000 parts by weight of pentane gas is added to surface of a tin plate to which had been added by spraying 1.15 grams of oil per 62,000 square inches of surface. Following evaporation of the pentane the rate of desorption of the radioactive material from the surface and from the contaminant was observed by use of a thin end window G.M. tube and counting system using a steady stream of filtered air as the evaporation agent. The rate of desorption or evaporation from the contaminated surface was significantly lower than when the similar procedure was carried out on previously cleaned tin plate. When Cir the same type of test was run on several different spots on the same piece of tin plate, various decreased rates of evaporation were observed showing that the spraying technique employed for laying down the oil film did not provide uniform coverage of the surface. Several oils were tested including dioctyl sebacate and cottonseed oil.

In a similar experiment, a solution of tetrabromoethane-C-14 in trifluorotrichloroethane in 1:60,000 ratio by weight was used to prove the presence of 6 milligrams per square foot of stearic acid on aluminum foil. The evaporation rate was always significantly lowered by the presence of contaminant and the results of several spot tests showed a decided unevenness in amount of stearic acid on the surface.

EXAMPLE VII Fifty lambda of a solution containing 0.5 microgram of tetrabromoethane-Cl4 in trichlorotrifluoroethane and substantially no nonvolatile residue was added, from a previously sealed 2 mm. (outside diameter) glass tubing, in which the solution formeda steady miniscus when inverted by breaking off first one end of the tube and then a second end, to a concavity in a stainless steel planchlet on which had been deposited previously 10 micrograms of linseed oil followed by curing in an air oven for twenty minutes at C. The results of observing the rate of evaporation using the equipment described previously showed values of 110, 92, 84, and 76 whereas the same determination in the absence of the linseed oil showed values of 60, 15, 7 and 4, respectively. When the test plate was cleaned in an ultrasonic cleaner for a period of eight minutes using trifluorotrichloroethane as solvent, a subsequent test showed that substantially all of the linseed oil had been removed when the values of 56, 14, 8, and 5, respectively were obtained. These values were obtained using the apparatus of the invention described in S.N. 506,566.

When the same test was performed with another ultra sonic cleaner, the results following the eight-minute cycle showed values of 70, 24, 13, and 8 showing that the second ultrasonic cleaner did not function as well as the first one.

When the same test was performed with yet another ultrasonic cleaner, the results showed that this third cleaner barely cleaned the surface at all; that is, the results following cleaning were 90, 78, 69, and 62.

Thus, the method of observing comparative rates of evaporation on previously similarly contamined surfaces permits an accurate and instrumental evaluation of the efficacy of ultrasonic cleaners.

In still another experiment a mixture of decyl bromide1-Br and nonanol-l-C is used as the radioactive element in order to effect preferential pickup by contaminants varying in chemical composition. It is noted that this combination works well with contamination containing both carbohydrates and hydrocarbonaceous materials. Similarly other mixtures of contaminants are treated with radioactive materials purposely compounded in mixtures to insure good pickup by each individual contaminant in the composite impurity.

EXAMPLE VIII Three parchment samples consist of the following: 1. Raw stock (bleached), 2. 1 Silicone treated (one side only), and 3. 1 Quilon treated one side only). Samples of each type of parchment are placed in a flat horizontal position and the test solution (0.05 microcurie of tetrabromoethane-C-14 in 100,000 parts of trifluorotrichloroethane) added. Following positioning of the detector just above the test surface and flowing nitrogen gas over the test surface, the evaporative rates are de termined numerically by analyzing sequential areas (A-D) under the evaporate curve (Counts Per Minute vs. Time) using a six-second time delay before start of A B C D (I) Top side 56 12 8 Other side 54 12 7 6 (II) Treated side. 52 70 101 76 Other side 50 8 6 4 (III) Treated side. 100 110 55 32 Other side 70 13 9 The shape of the evaporation curve is indicated by the relative values of the various areas and the actual rate is shown by the values themselves. A fast evaporative rate is indicated by rapid peaking and. subsequent falling off to background levels (i.e., 3-4). The lack of penetration of the test solution into the raw stock is indicated by small numbers in the B areas. The raw stock parchment is substantially free from miscible organic residues and is substantially impervious to the test solution. Both sides of the raw stock test similarly. The silicone in the treated parchment alters massively the rate of evaporation of the test solution and the shape of the evaporative curve shows delayed peaking under the test conditions used. The test was in each instance repeated three times, and the sum of the areas (A+B+C+D) each time was consistent (299, 300, 298), thereby demonstrating uniformity of coating. The tests on the back side show that no silicone resin penetrated through the parchment. Quilon is also detected; the shape of the evaporative curves shows rapid peaking and rapid falling off towards background. This difference is due to different solubility relationships for the radiochemical/solvent/Quilon as compared to radiochemical/ solvent/ silicone. A small but significant amount of the Quilon appears to bleed through to the back side of the parchment. In many other measurements of silicone resin treated parchment, it is observed that the rate of evaporation is an indirect function of the amount of resin added to the parchment; that is, the rate is faster with smaller amounts of resin.

This experiment demonstrates that one may measure penetration of material added to fibrous articles both as to the kind of material as well as its amount.

EXAMPLE IX (A) Using the technique described in Example VIII above, 20 lambda quantities of tetrabromoethane-C-l4 (0.05 microcurie C-14, specific activity 85 millicuries per millimole) dissolved in 100,000 parts of trifluoro--trichloroethane is deposited onto a double sheet of toilet tissue (Scott Paper Company Soft-'Weve) which is positioned in a horizontal stretched condition (for example, by means of a sewing hoop) and a thin end window G.M. tube detector placed immediately adjacent and above the deposited radioactive labeled material. Con-trolled nitrogen gas is flowed both between the detector and the tissue surfaces and up through the paper system from underneath. Using the method of data interpretation described in my copending application S.N. 506,566, sequential areas under the evaporation curve are obtained as follows: A-54, B-l2, C4, and 'D-3 indicating rapid and complete evaporation of the radioactive material from this surface system.

When this experiment is repeated using a wet strength paper system of similar construction and weight (Scott facial tissue), a typical evaporation rate obtained is A-64, B-l8, C6, and D4, thereby demonstrating (particularly the A, B, and C values) that the second paper system possesses a significant amount of organic residue in addition to the cellulosic fiber system of the first paper systerm.

Since the evaporative response is quantitative with respect to the amount of resin deposited into the paper system, with proper calibration based on known amounts of resin, this method is used to determine and measure the amount of resin deposited in any standard process.

This experiment also demonstrates the passage of the gas controlling evaporation through the surface system being tested to effect more uniform and more complete evaporation.

(B) When samples of Kraft paper (to which has been added 5 lbs. of fluorocarbon acids per ton of paper) are examined, the nitrogen being flowed only between the surface of the paper and the detector system and not through the Kraft paper because of its lack of porosity, the presence of organic residues both as to amount and kind are still readily determined by the reference to suitable standards by comparing the rates of evaporation of tetrabrornoethane C-14 as previously described or of tridecane-C14 or of the dimethyl ether of triethylene glycol-C-14 or of other suitable labelled radioactive material, particularly using solvents such as cyclopentane or diethyl ether to apply the labeled material.

In general, the rate of evaporation of these materials from nontreated Kraft paper surface systems is not as complete as it is from the nontreated parchments of Example VIII, since the surface systems are much more complex; migration and penetration into the complex interstices by the radiochemical test solutions result in a longer period for the solutions and their components to migrate back out and to evaporate. In addition, the specific absorptive desorptive phenomena associated with the cellulosic fiber system and the particular radio chemicals involved further tend to restrict or alter the rates of evaporation observed with nonporous flat and horizontal surfaces.

(C) Bond papers are also examined by the technique described in Example VII and the amount of slip agent, release agent or other organic residue additive determined by measuring the rate of evaporation of the added radioactive labeled test material or materials from the surface system and by comparing the observed rate with the rate established in the absence of added residue and the rates established for known levels of added residue. Bond papers, in general, do not permit evaporation to the extent observed with clean parchment since the accessible matrices on the bond cellulosic surfaces are much more complex and permit penetration by the radiochemical solutions to a greater extent. However, the effects of added stearic acid, silicone resins or other similar materials are measured and differentiated from the nontreated bond matrices. Based on the data interpretation as described in my copending application, S.N. 506,566, now Pat. No. 3,412,- 247, the numerical values based on tridecane C-14 (0.05 microcurie, millicuries per millimole in 100,000) parts of high purity cyclopentane tested in ambient temperatures are:

for untreated bond-74, 47, 41, 36; for bond with .5% stearic acid-89, 66, 53, 46;

on each side.

(D) Inorganic fillers are oftentimes used in paper manufacture to alter the density, slip characteristics, printability and other properties of paper compositions. Such materials are discribed elsewhere in this and my copending applications for varying absorptive and desorptive effects on added radiochemical mixtures as regards the evaporative rate phenomena associated with the radiochemical. Based on test solutions such as are described in Experiment VIII above, the presence and amount of such fillers and extenders are determined by measuring the rate of evaporation of the added radiochemical test solutions and quantitative information is obtained by comparing rates to the rates established from papers containing known and standard quantities deposited in and on such matrices.

7 EXAMPLE X deposited on woven cotton and other fabrics; an orderly reduction in evaporative rate is observed using standard test technology as described elsewhere in this application and passing nitrogen gas up through the fabric as well as across and between the fabric and the detector. In measuring similar cotton fabrics containing no resin, and 1, 2, 3, and 4 percent of the resin based on the weight of the fabric, the evaporation rate was fastest for the clean scoured cloth containing no resin and progressively was slowed with increasing resin content. Similar results are obtained with wools and wool synthetic blends thus providing a rapid method for direct measurement of such fabric modifying systems. Ethylene urea/formaldehyde resins, when deposited on cotton synthetic fabric blends containing 50% cotton and 50% polyester fibers, are quantitatively measured by this evaporative rate technique when compared with untreated similar fabrics. Crosslinking does not appreciably affect the evaporative response of added tetrabromoethane-C-14 in trifluorotrichloroethane solvent test solutions; that is the evaporative rate established prior to cross-linking is substantially similar to the evaporation rate obtained after cross-linking thereby permitting a nondestructive test of the amount of resin still present in a fabric system following the crosslinking step.

EXAMPLE XI Application of evaporative rate measurements of an added test chemical solution is used to determine the weight percent of finish on synthetic and natural fibers. These measurements are made on fibers in woven webs and in yarn bundles and on individual monofils either cut into short lengths and deposited into linear concavities on clean glass slides or uniformly stretched between two points with the solution being permitted to wick into the stretched fiber system or in other ways. The measurement of finish level from less than 0.1 weight percent to more than 5 weight percent on cotton, polypropylene, nylon, polyester, acetate rayon and other similar synthetic fibers are made using techniques above described. Using the sequential area method for interpretation of evaporative rate data, typical results which were obtained using tetrabromoethane-C14 in trifluorotrichloroethane as used above are as follows:

(1) Drawing polypropylene yarns (approximately 600 denier) stretched under constant tension and laid down on a slightly concave glass slide and the test solution was added. After wicking has occurred, the slide was removed, and the following A through D values were obtained:

(2) Tests run on 75-denier 20-count acetate rayon in which inch lengths were cut and positioned and tested in a glass concavity.

The above data show the orderly change in evaporative response with increasing amounts of surface modifiers.

EXAMPLE XII When aluminum foil samples on which is deposited dioctyl sebacate in amounts of 0.15, 0.5, 1.5, 5.0, and 10.0 micrograms per square centimeter are examined using the technique described in Example III, the rate of evaporation obtained is an inverse function of the amount of deposited residue; that is, the greater the amount of residue, the slower the rate of evaporation. Similar results are obtained with stearic acid on aluminum and with other lubricants placed on aluminum foil commercially for lubrication and other purposes.

The aluminum foil is held mechanically in such a way (reduced pressure is applied below the foil sample) that a slight dishing of the foil occurs to insure uniform positioning of radiochemical test solutions. When aluminum sheet is used in place of foil, it is sometimes of advantage to dimple the sheet mechanically to aid the controlled evaporation and to prevent runoff in the event the sheet is not maintained in an absolutely horizontal position.

EXAMPLE XIII Direct measurement of lubricant oils, silicones, ammonium stearate, stearic acid and other types of organic residue applied commercially on glass surfaces are made readily and reproducibly by means of the evaporative rate technique using an added radiochemical test solution. The decrease in evaporating rate is a function of the orderly increase of the amount of residue.

EXAMPLE XIV In my copending application, S.N. 607,873, filed Jan. 9, 1967, filed concurrently herewith, determination of the active sites by absorption/desorption effects and thereby a function of surface area is described for finely divided talc; the evaporative response of applied radioactive labeled material solutions from the talc is measured. Based on performance and independent surface area measurements by gas absorption techniques, the validity of evaporative rate measurements as a function of surface area is established. When similar talc is exposed to a small amount of a perfume additive (an organic odor producing material) and the test is repeated, the presence of the perfume significantly alters and slows the observed rate of evaporation. This test was run on plant production material sold commercially as talcum powder, This example shows that the surface being tested may be particulate as well as fiat horizontal and the presence of organic residues detected and measured.

EXAMPLE XV The level of cleanliness and/or the existence of deliberate residues on printed circuit boards are conveniently measured by means of the evaporative rate technique described in this application. Thus, the presence of unwanted solder flux or residues following mounting and soldering functions are readily determined and the quantities measured through the use of tridecane-C-14 dis solved in cyclopentane since rosin flux residues are readily dissolved in the cyclopentane and the determination is sensitive down to a very small fraction of a microgram. Unwanted and unexpected contaminants such as fingerprints may readily be detected and measured by the same technique.

EXAMPLE XVI Determination of the extent of the cross-linking step in the curing of epoxy and other resin systems on surfaces may be accomplished through the proper application of the evaporative rate technique. Thus, using tetrabromoethane-C-14 dissolved in trifiuorotrichloroethane followed by measuring the evaporation in a metered stream of dry gaseous nitrogen provides useful information relative to the extent of cure. Non-cross-linked or noncured materials act as residues on the surfaces since they in part dissolve in the solvent systems employed; as curing progresses, the solubility of these residues decreases and the evaporative rate increases so that with a fully cured film system, the evaporative rate appears substantially identical to the evaporative rate from a clean fresh surface. Numerical expressions of evaporative rate based upon epoxy resins as described in my copending application S.N. 506,566 are:

A B C D Non-cross-linked 140 138 142 139 Partially cross-linked-.- 130 108 91 94 Highly cross-linked 60 15 8 6 Bloom in elastomeric and migration of low molecular Weight additives and plasticizers in plastic materials are measured as residues on the surfaces of elastomers and/ or plastics by the evaporative rate technique of an added radioactive labeled test solution as described elsewhere in this application. For maximum sensitivity and detectability, it is essential that the radiochemical and/or solvent system used does not penetrate and dissolve into the elastomer or plastic surface itself since such migration or solution makes the surface appear as a residue insofar as the rate of evaporation measurement is concerned. The blooming and migrating materials tend to be of lower molecular weight and therefore are more readily soluble in the solvent/radiochemical systems customarily used.

EXAMPLE XVIII With film forming materials such as low density polyethylene in an extremely thin film, the thickness of the film may be determined by the technique of this application, through the proper selection of the radioactive labeled material and the low boiling solvent. When a solvent for polyethylene is used as the solvent for the radiochemical, the polyethylene film acts as a residue on a suitable inert substrate rather than as a new surface and the rate of evaporation of the test solution therefore is a function of the thickness of such a layer.

EXAMPLE XIX Deliberate additives to increase printability and/or to modify adhesion characteristics of plastic films such as polyester films, cellophane, polypropylene and others may be measured by the evaporation rate technique in which the substrate film acts as the surface being examined and the deliberate additives as the residue. In measuring and evaluating such films it is of value to examine them in such a way that they are held in a slightly concave configuration, for example, by pulling a slight vacuum at the center of a 2" disc so that the test solution always centers uniformly and so that the area covered by the test solution is uniform from test to test.

EXAMPLE XX Parting or mold release agents such as organic waxes, silicones and the like, are used to permit ready and facile separation of electrodeposited materials from metallic electrodes. The uniformity of such coatings obviously affects the ease with which such parting is carried out. Application of the evaporative rate technique described in this application is used to measure the uniformity of such parting agents and therefore to improve the predictability of the parting process. Mold release agents are used to provide improved release of molded objects from the dies and forms used for their manufacture. Following forming, their presence, however, oftentimes is deleterious for additional steps such as painting, coating or bonding and they must be removed by suitable cleaning processes. Determination of the quantitative distribution of such agents on surfaces of molded articles is carried out through application of evaporative rate analysis of an added radioactive labeled test solution. The greater the amount of mold release agent remaining on the tested surface, the more slowly does the evaporation proceed under standard test conditions.

In Example VIII of my cOpending application entitled Selective Detection and filed concurrently herewith, there is disclosed a specific example of the measurement of the removal of a wax from a surface by solvent extraction.

In all of the above examples the chemical detections are of exceedingly high purity. For example, the radiochemicals, even though used in extremely small, for example, submicrogram quantities per test, are substantially free of nonvolalite materials. The solvents, if used, contain less than 1 ppm. of nonvolatile materials. Thus, the materials used do not add deposits to any extent that would lead to invalid conclusions.

While the above examples adequately describe various conditions and applications, it is to be appreciated that there are a number of modifications and equivalents that apply to the invention and that such can be found in the previous applications from which this application stems and which are identified above. Those teachings are incorporated here by reference to those applications. However, this application is not limited thereto for there are other extensions. For example, by the processes of this invention one may determine the extent of penetration of medicinals, oils, and the like into the skin of animals and the extent of removal of such materials by cleaning or washing techniques. So also, one may determine the amount of moisture adsorbed or desorbed on articles under changing conditions of humidity. As is well known, the amount of moisture on a given surface may mean the success or failure of a step to. be taken such as adhesively bonding or laminating that surface to another. From the above it can be seen that the processes involved in this invention relate to absorption and adsorption or to sorption or retention of certain materials by other materials.

I claim:

1. A process for monitoring an operation in which a chemically reactive material is to be produced in a desired manner which process comprises selecting representative material being produced in the operation; contacting said selected material with a radioactive chemical with is selectively retained by at least a part of said material and which leaves the said material by evaporation; measuring the rate at which said evaporation of said chemical occurs, thereby measuring the retention of said chemical by said material; and comparing the results obtained with control determinations, thereby determining, as compared to the control, the state of the chemical reactivity of said material produced in said operation.

2. A process in accordance with claim 1 in which said representative material is fibrous in nature.

3. A process in accordance with claim 1 in which said representative material is nonfibrous in nature.

4. A process in accordance with claim 3 in which said nonfibrous articles are powdered materials.

5. A process in accordance with claim 1 in which said production involves polymerization reactions.

6. A process in accordance with claim 5 in which said polymerization reactions involve cross-linking reactions.

7. A process in accordance with claim 1 in which said chemical is placed on an article which is porous.

8. A process in accordance with claim 7 in which said porous article is fibrous.

References Cited UNITED STATES PATENTS OTHER REFERENCES Electronic Industries, November 1959, vol. 18, No. 11, pp. 110, 246, Fighting Flux Contamination.

MORRIS O. WOLK, Primary Examiner R. M. REESE, Assistant Examiner US Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,560,157 February 2, 19

John Lynde Anderson It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 36, "The" should read This line 43, "issued November 9, 1968" should read issued November 19, 1968 line 49, after "rapid" insert and line 55, "examnied" should read examined line 66, "sa" should read as Column 3, line 13, "forcepts" should read forceps line 41, "precense" should read presence line 45, "conditiaions" should read conditions Column line 66 should read only) and 3. "l" "Quilon" treated (on: side only). Sam- Column 6, line 16, cancel "the"; line 46 "on" should read of Column 7, in Example XI, column C Reads: should read 5 5 l3 l3 13 13 l4 14 25 15 Signed and sealed this 17th day of August 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, Attesting Officer Commissioner of Pate