US2795132A

US2795132A - Apparatus for measuring gas in molten metals

Info

Publication number: US2795132A
Application number: US496808A
Authority: US
Inventors: Robert M Boehme; Richard B Lawrance
Original assignee: National Research Corp
Current assignee: National Research Corp
Priority date: 1955-03-25
Filing date: 1955-03-25
Publication date: 1957-06-11
Anticipated expiration: 1974-06-11
Also published as: DE1046914B

Description

1, 1957 I R. M. BOEHME ErAL 2,795,132

APPARATUS FOR MEASURING GAS IN MOLTEN METALS v Filed March 25, 1955 z Shuts-Sheet 1 FIG.

' INVENTORS Ram M. BMW

BY Aiduxl'd, Paul mug ATTORNEY June 11, 1957 R. M. BOEHME ETAL 2,795,132

APPARATUS FOR MEASURING GAS IN MOLTEN METALS Filed March 25, 1955 2 Sheets-Sheet 2 l9 To Vacuum Pump 7 F13 j L i r-fifim l4 BY Rkwu-cl. 73. Lawmmcc OM ATTORNEY United States Patent This invention relates to measuring and in particular to the quantitative measurement of hydrogen contained in metals and alloys".

principal object of this invention is to provide an apparsin for rapidly'and accurately measuring the quantity of hydrog n contained in metals and alloys.

other objects or the invention win in part be obvious andwill in p art appfear hereinafter.

The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts, and the method involving the sevsuch steps' withresp'elct to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims;

Fora fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the followin'gdrawings wherein; Y

Fig. 1 is a schematic diagram illustrating one preferred apparatus embodying the invention; and

Fig. 2 is an enlarged fragmentary view of a portion of Fig. l.

The demand for high purity titanium and zirconium and alloys rich in these metals has been rapidly increasing. The recent interest in titanium and zirconium and alloys thereof of very high purity has necessitated the development-of a rapid and accurate method for determining the quantity of residual hydrogen in these metals, since appreciable quantities of hydrogen have been found to have a detrimental e'fiect on the properties of such metals and alloys so as to restrict their usefulness. The traces of hydrogen,- which may be either dissolved in the metal o'r 'in actual chemical combination, have been shown to increase the brittleness of the metals and thus seriously aflfec't such properties as the ductility and impact strength.

Heretofore, it was proposed to use either a vacuum fusion method or aho't vaeuu'fn extraction method for determining the residual hydrogen in titanium and z'i'rconium and alloys rich in these metals. The vacuum fusion method basically consists in melting the metal,

reducing any metal oxides with carbon and thermally decomposing any nitrides and hyrides therein, and subsequently rapidly removing the resulting gases carbon monoxide, nitrogen and hydrogen. The. total pressure of the gases. evolved is measured in a known volume by means of a McLeod gauge. The evolved gases are then oxidized to carbon dioxide, nitrogen and water. The pressure of the gases carbon dioxide and nitrogen is measured in a known volume by means of a McLeod gauge, and the pressure attributable to hydrogen is determined as the difference between the two pressure readings. The volume and pressure 'of the hydrogen being known, the quantity of hydrogen in themetal is then determined by application of the ideal gas law. The vacuum fushion method, however, is not entirely satisfactory for such er'al step's and the relation and the order of one or more determinations, since it necessitates rather elaborate ap- 2,795,132 Phtented June 11, 1957 2 paratus, long. analysis times, and somewhat. decreased accuracy of result as hydrogen constittues but a part of the total gas evolved from. the metal. 7

The hot vacuum-'extract'ion-method consists in heating a metal sample, at a temperaturewhich is sufiiciently high to evolve only the hydrogen but which is below the: melting point of the metalu Although the hot vacuum extraction method evolves only hydrogen from'zirconium and titanium and alloys thereof, the. several existing analytical procedures based on this-method exhibit such undesirable aspects as excessively longoutgassing periods and potentially erroneous results, due to the continued evolution of hydrogen from previous samples retained within the heating zone. The present invention eliminates such undesirable aspects through the useof a novel apparatus.

The apparatus of the present invention comprises furnace means for hot vacuum extracting hydrogen from lection system of known volume, means for measuring the pressure of hydrogen in the gas collection system, and means for evacuating the gas collection system. The furnace means preferably'comprises a head chamberi-n open communication with the upper end of an-elongated cylindrical oven chamber of substantially uniform cross section, a third chamber of substantially greater cross section than the oven chamber joined to the lower end of the ovench'amber and in open communication therewith, and a spent sample collection chamber joined, to the lower end of third' chamber and in open communication therewith. The oven chamber contains therein a metal crucible which has a. melting point above 1500 C. and which will neither 'fuse nor alloy with the sample to be analyzed. In preferred embodiments, this crucible may consist of either thoria-coated molybdenum or thoriacoated tantalum, The cr'ucible is preferably attached to and positioned between hollow centering means and is preferably heated by rneansof an induction coil which surrounds a portion of the oven chamber. The head chamber preferably contains at least one sample arm and means for holding the cruc-ible within that portion of the oven chamber surrounded by the induction heating means and for moving the crucible toand from the third chamber, the third chamber being provided with means for tipping the crucible which causes the metal or alloy sample to drop therefrom into the spent sample collection chamber.

Without intending-to limit the scope thereof, the method of the present invention will be initiallydescribed in connection with the analysis of titanium, zirconium, uranium andalloysrich these metals. The method comprises evacuating an oven and gas collection system of known volume to a pressure below about 10- mm. Hg abs, then seali g-th'e gas collection system from the 'evac'uating means; add-ing to a crucible contained .within an oven, which is of substantially uniform cross section, a sample selected from the group consisting of titanium, zirconium, 'uranium'andalloys rich in these metals; heating the sample to "a temperature which is sufficiently high to evolve onl'yhydr'o'gen but which is below the melting point of the sample, the preferred temperatures ranging between about 750 C. and 1500 C.; c'ollecti-ngthe evolved hydrogen in the gas collection system; measuring the pressure of the hydrogen in the collection system, then opening the collection system to the evacuating means to remove the collected hydrogen; moving the crucible into a chamber of substantially greater cross section 'then'the oven "and 'tippi-ng the crucible in the latterc'hamher to drop the'sample'which has been analyzed into a spent sample collection chamber, moving the empty crucible back to the "oven; sealing the gas collection system means which is.comprised in part of chambers 10a,

10b, 10c and 10d. The head chamber 10a is joined at its lower end by meansof aground tapered joint to,.the.

upper end of chamber 10b. The elongated cylindrical chamber 10b, servesas'an oven of uniform cross section, and is joined at its lower'end by means of alground 'tapered joint to chamber 100, which is of substantially greater cross section .than oven 10b. Chamber 100 is preferably constructed so as to have a. cross section which is on the order of about three times the cross section of oven 10b. Chamber 100 is joined at itslower end by means of a ground tapered joint to a spent sample collection chamber 10d. Although the furnace means 10 is illustrated in part as four chambers joined by ground tapered joints, it is also possible to construct it with fewer chambers. For instance,

chambers

10c and 10d may be constructed so as to constitute one chamber which can be joined to oven 10b by means of a ground tapered joint. It is highly desirable that atleast one ground tapered joint be included in the lower portion of furnace means 10 so as to provide a means for readily removing analyzed samples which are deposited and collected in the lowest chamberdeSignated here as 10d. It is also desirable that oven 10b be provided with ground tapered joints at its ends so that it may be easily replaced or removed for cleaning. Chambers lob, 10c and 10d are preferably formed of either fused silica or Vycor, while all the other parts of the apparatus are preferably fabricated from Pyrex glass.

Chamber 10a is provided with a plurality of side arms. Arm 12 connects chamber 10a with a mercury diffusion pump 34. Loading arm or sample arm 14, shown loaded with samples 15, is provided with a loading port 16 which, during operation, is closed by means of glass cap 17. A small magnet 18 is used to operate the iron pusher 19 within the sample arm 14. Although only one sample arm is illustrated, it is preferable to equip thehead chamber 10a with several of such arms so that an abundance of samples can be loaded into the arms to permit long continuous analytical operations. Am 20 contains means for holding the crucible 22 within the induction heating zone of oven 10b and for moving the crucible 22 to and from chamber 100.

Within the oven 10b, there is positioned a crucible 22 in whichthe samples to be analyzed areheated. The heating is preferably performed by means of an induction heating coil 24, although other means such as resistance heating may be used. The crucible 22,'is of smaller diameter than the oven 10b and is preferably constructed of a material which has a melting point above 1500' C., and which will not outgas appreciably nor fuse nor alloy with the sample to be analyzed in the temperature range below. 1500 C. In preferred embodiments of the invention, the crucible is preferably constructed of tantalum of molybdenum coated on their inner surfaces with thoria. These crucibles have been found to be most satisfactory in the analysis of titanium and zirconium, since samples of these metals neither fuse nor alloy with such crucibles and thus are capable of being freely removed from the crucible 22 after-they have been analyzed. The crucible 22 is centered in oven 10b by means of hollow

metal centering cylinders

26 and 26a, which are also of just slightly} smaller diameter than oven 1012 but of a larger diameter than crucible 22. Centeringcylinders 26 and 26a are attached to crucible 22 by means of chains or wire and are preferably constructed of a magnetic material. Centering cylinder 26 "is connected by means of a chain or wire to a counter weight 28 which supports the crucible 22 and the, centering

cylinders

26 and 26a within oven 10b. Counter weight 28 located in arm .20

is preferably made of a magnetic material so thatfit may trated here for moving counter weight 28 andthus crucible 22 and centering cylinders .26 and26a, other means may be employed for effecting this movement.

A right angle prism for reading the sample tempera ture by means of an optical pyrometer. is located at the upper end of the chamber 10a, and the sample is accordingly viewed through the hollow centering cylinder 26.

Arm 12, which connects chamber 10a with a mercury diffusion pump 34, is preferably provided with a palladium leak 36 which is. used in calibrating the Pirani gauge 38 for hydrogen. The Pirani gauge, which provides a convenient means for following the variations in pressure in the gas collection system, is connected to a strip chart recorder 40, also the Pirani gauge being composition sensitive and calibrated here for hydrogen. If gases other than hydrogen are being evolved, this fact will be detected since the Pirani gauge will give a reading lower than that given by the McLeod gauge which indicates total gas pressure. Strip chart recorder 40 graphically indicates the pressure changes in the system due to the evolution of hydrogen gas from the samples and permits the operator to observe when the evolution of hydrogen has been completed. This method of measuring also advantageously provides a permanent record of the sample analysis.

The total gas collection system is bounded by the mercury ditfusion pump 34 on one side and the mercury cut-off indicated at 52. The gas collecting system of known volume comprises a manifold 42, a small collection bulb 44, a McLeod gauge 46 which is in direct communication with bulb 44, large. collection bulbs 48, and mercury cut-olfs 50 and 52. The mercury for the McLeod gauge 46 and cut-oifs 50 and 52 is supplied from

mercury reservoirs

54,56 and 58 respectively. Mercury cut-oifs are preferred since mercury neither absorbs nor gives oif gas during use. Although mercury cut-offs are illustrated, it is also possible to construct the system so that stop cocks may be used. The gas collection system is exhausted by means of an oil diffusion pump 60 and mechanical pump 62.

In carrying out the analytical procedure, solid samples of known weight, which may be in the form of approximate spheres, cylinders, parallelepipeds or cubes, arefirst cleaned and degreased. Powder, turnings, drillings and the like are preferably encased in an outgassed tantalum capsule. The ends of the tantalum capsule are slitted or perforated so as to permit the free evolution of hydrogen from the sample within. A number of samples areloaded into sample arm 14 through load port 16. All the glass joints in the system, as well as the joint between the glass cap 17 and arm 14, are sealed by means of a non-gassing hard wax.

The mercury is lowered from cut-

offs

50 and 52. The mercury diifusion pump 34, oil diffusion pump 60, and mechanical pump 62 are started, so as to evacuate the whole system to a pressure below about 10 mm. Hg

abs. When the desired operating pressure has been attained, the mercury from

reservoirs

56 and 58 is raised into cut-

offs

50 and 52 by means of compressed air or carbon dioxide or other means (not shown in diagram), so as to provide a gas collection system bounded by mercury diffusion pump 34 on one side and mercury cut-oif 50 on the other side.

A sample is pushed from the arm. 14 by the iron pusher 19 manipulated by magnet 18. The sample passes into chambers 10a and 10]) through the hollow centering cylinder 26 and into crucible 22. Means other than magnetic may be employed for feeding samples to the crucible. The crucible 22 is then preferably heated by means of an induction heating coil 24 to a temperature at which only hydrogen evolution will take place but which is below the melting point of the metal sample.

The temperature, depending upon the; melting point of the sample, may be varied Between about 750 C. and 1500 C. Generally, the higher the temperature, the more rapid the evolution of hydrogen from the sample, and thus the shorter the time required for analysis. In the determination of hydrogen in samples of titanium, zirconium and alloys rich in these metals, temperatures on the order of about 1400 C. are prefered. In the case of metals having a melting point above 1500 C.', temperatures below 1500" C. can be employed. However, in such cases longer hydrogen evolution periods are required, since the rapidity of hydrogen extraction is to a great extent dependent on sample temperature. The crucible 22 and sample therein are brought to the operating temperature very quickly, and the hydrogen which evolves rapidly is collected in the above defined gas-collecting volume. If too much gas is present to measure in this volume, the mercury in cut-off '50 is lowered so as to allow the gas toexpand into the larger collection volume which now includes bulbs 48. The hydrogen extraction is usually complete within five minutes.

Two methods of determining the amount of hydrogen evolved may be employed. The first method contemplates reading, by means of a McLeod gauge, the final pressure of the evolved gas collected in the known volume and then determining the quantity of hydrogen liberated from the metal by application of the ideal gas law. The second, and preferable, method contemplates observing, by means of a Pirani gauge, the variations in the pressure of the gas collection system due to the evolution of hydrogen and graphically recording these pressure changes on a strip chart. Thus a graphic means which indicates when the evolution of hydrogen has been completed also provides a permanent record of the sample analysis. The recordings are preferably calibrated so as to give a direct reading of the micrograms of hydrogen evolved. Thus all that need be done is to" divide the'micrograms of hydrogen evolved by the sample Weight expressed in grams to determine the parts per million of hydrogen in the sample.

After the readings are taken, the induction heater Z4 is preferably shut off and the mercury cut-offs 50' and 52 are opened. The collected hydrogen is then pumped out by means of diffusion pump 60 and mechanical pump 62. The counterweight 23 is moved up and 2th by means of magnet 30 as illustrated in Fig. 2. This causes the crucible 22 and the centering

cylinders

26 and 26a in oven b to be lowered into chamber 100. ,When centering cylinder 26a is lowered into chamber 100, it is attracted to and secured upon the wall thereof by means of magnet 25. Upon further lowering of crucible 22 into chamber 100, it is tipped so that the analyzed sample a drops therefrom into the spent sample collection chamber 104. Means other than magnetic may be employed to tip the crucible 22 in chamber 10c. As the counterweight 28 is moved back down arm to retract the crucible and centering cylinders into oven 10b, centering cylinder 26a is released from the wall of chamber 100. After the crucible 2?. is positioned within the induction heating zone of oven 10]), the mercury cut-oifs 50'a'nd 52 are closed, another sample is dropped into the crucible (passing through the hollow centering cylinder 26), and the procedure is repeated until all the samples in arm 14 have been analyzed.

Although the invention is particularly directed to the analysis of hydrogen in titanium, zirconium, uranium and alloys rich in these metals, it is also applicable for the determination of hydrogen in other metals in those cases where only the hydrogen is liberated from the metal by heating to a temperature below its melting point in a vacuum.

The present process and apparatus presents many advantages over other processes and apparatus in the field. For instance, the present invention provides for:

(a) The use of a small crucible for holding but a single sample.

(b) Minimum power loss by heat radiation. Thus only a single comparatively small induction unit is needed.

(c) No interference from previously analyzed samples since the sample is removed from the crucible after being analyzed. if the samples were allowed to accumulate in' the crucible, they would necessarily be subjected to many heating operations which would cause some evolution of gas therefrom and would interfere with and render uncertain the analysis of the" current sample.

d) Minimum preliminary outgassing since the crucible and furnace assembly are constructed of materials which do not outgas appreciably, and since the principal parts can readily be moved into the induction heating zone for individual outgass'ing.

(e)' A short time for hydrogen removal from the sample.

(f) A furnace which is readily disassembled, economical to construcgeasy to' clean, and convenient to handle.

,(g) Affords a direct means for calculating the quantity of hydrogenin the sample by graphically recording and observing .the'evolution ofhydrogen from the sample. This also provides a permanent record of the sample analysis.

(h) A reusable refractory capsule. (tantalum) for retai'ning chips, wires, drillings, turnings, etc.

Since certain changes may be made in the above process and apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description, or shown in the accompanying drawings, shall be interpreted as illustrative and riot in a limiting sense.

What is claimed is: A p

1. An apparatus for determining the quantity ofhydrogen in metals and alloys which during operation is closed to' the atmosphere comprising a head chamber containing at least one sample arm in open communication with the upper end of an oven chamber, a third chamber of substantially greater cross section than said oven in open communication with the lower end of said oven, said oven containing therein a crucible which has a melting point above about 1500 C. and which will neither fuse nor alloy with the sample to be analyzed, means cooperating with said sample arm for transferring samples from said arm to said crucible, heating means surrounding a portion of said oven, means within said head chamber for holding said crucible within that portion of said oven surrounded by said heating means and for moving said crucible to and from said third chamber, said'third chamber being provided with means for removing the analyzed sample from said lcrucible to the bottom of said third chamber, pump means for evacuating the evolved hydrogen from said chambers into a' gas collection system of known volume, means for measuring the pressure of hydrogen in said gas collection system and means for evacuating said gas collection system.

2. An apparatus for determining the quantity of hydrogen in metals and alloys which during operation is closed to the atmosphere comprising a head chamber containing at least one sample arm in open communication with the upper end of an elongated cylindrical oven cham-' ber of substantially uniform cross section, a third chamber of substantially greater cross section than said oven chamber in open communication with the lower end of said oven chamber, and a spent sample collection chamber in open communication with the lower end of said third chamber, said oven chamber containing therein a crucible which has a melting point above about 1500" C. and which will neither fuse nor alloy with the sample to be analyzed,- means for centering said crucible in said oven chamber, means cooperating with said sample arm for transferring samples from said arm to said crucible, heating means surrounding a portion of said oven chamber, means within said head chamber for holding said crucible within that portion of said oven chamber surrounded by said heating means and for moving said crucible to and from said third chamber, said third chamber being pro vided with means for tipping said crucible to cause the analyzed sample to drop therefrom into said spent sample collection chamber, pump means for evacuating the evolved hydrogen from said chambers into a gas collection system of known volume, means for measuring the pressuretof hydrogen in said gas collection system and means for evacuating said gas collection system.

3. An apparatus for determining the quantity of hydrogen in metals and alloys selected from the group consisting of titanium, zirconium, uranium and alloys rich in these metals, which during operationis closed to the atmosphere comprising a head chamber containing at least one sample arm in open communication with the upper end of an elongated cylindrical oven chamber of substantially uniform cross section, a third chamber of substanti'ally greater cross section than said oven chamber in open communication with the lower end of said oven chamber, and a spent sample collection chamber in open communication with the lower end of said third chamber, said oven chamber containing therein a crucible selected from the group consisting of thoria-coated tantalum and thoriacoated molybdenum, means for centering said crucible in said oven chamber, the opening from the sample arm being positioned directly above the oven chamber so that a sample pushed from the sample arm by a pushing means can fall into the crucible while it is centered in the oven chamber, heating means surrounding a portion "of said oven chamber, means within said head chamber for holding said crucible within that portion of said oven chamber surrounded by said heating means and for moving said crucible to and from said third chamber, said third chamber being provided with means for tipping said crucible to cause the analyzed sample to drop therefrom into said spent sample collection chamber, pump means for evacuating the evolved hydrogen from said chambers into a gas collection system of known volume, means for measuring the pressure of hydrogen in said gas collection system and means for evacuating said gas collection system.

4. An apparatus for determining the quantity of hydrogen in metals and alloys selected from the group consisting of titanium, zirconium, uranium and alloys rich in these metals, which during operation is closed to the atmosphere comprising a head chamber containing at least one sample arm in open communication with the upper end of an elongated cylindrical oven chamber of substantially uniform cross section, a third chamber of substantially greater cross section than said oven chamber in open communication with the lower end of said oven chamber, and a spent sample collection chamber in open communication with the lower end of said third chamber, said oven chamber containing therein a crucible selected from the group consisting of thoria-coated tantalum and thoria-coated molybdenum, said crucible being attached to and positioned between hollow centering means, means cooperating with said sample arm for transferring samples from said arm to said crucible,heating means surrounding a portion of said oven chamber, means within said head chamber for holding said crucible that portion of said oven chamber surrounded by said heating means and for moving said crucible to and from said third chamber, said third chamber being provided with means for tipping said crucible to cause the analyzed sample to drop therefrom into said spent sample collection chamber, pump means for evacuating the evolved hydrogen from said chambers into a gas collection system of known volume, means for measuring the pressure of hydrogen in said gas collection system and means for evacuating said gas collection system.

5., Apparatus of claim 3 wherein said elongated cylindrical oven chamber is comprised of a glass selected from the group consisting of Vycor and fused silica.

6. An apparatus for determining the quantity of hydrogen in metals and alloys selected from the group consisting of titanium, zirconium, uranium and alloys rich in these metals which during operation is closed to the atmosphere comprising a head chamber containing at least one sample arm in open communication with the upper end of an elongated cylindrical oven chamber of substantially uniform cross section, a third chamber of substantially greater cross section than said oven chamber in open communication with the lower end of said oven chamber, and a spent sample collection chamber in open communication with the lower end of said third chamber, said oven chamber containing therein a crucible selected from the group consisting of thoria-coated tantalum and thoria-coated molybdenum, means for centering said crucible in said oven chamber, means cooperating with said sample arm for transferring samples from said arm to said crucible, induction heating means surrounding a portion of said oven chamber, means within said head chamber for holding said crucible within that portion of said oven chamber surrounded by said induction heating means and for moving said crucible to and from said third chamber, said third chamber being provided with means for tipping said crucible to cause the analyzed sample to drop therefrom into said spent sample collection chamber, pump means for evacuating the evolved hydrogen from said chambers into a gas collection system of known volume, McLeod gauge means for measuring the pressure of hydrogen in said gas collection system and means for evacuating said gas collection system.

7. An apparatus for determining the quantity of hydrogen in metals and alloys selected from the group consisting of titanium, zirconium, uranium and alloys rich in these metals which during operation is closed to the atmosphere comprising a head chamber containing at least one sample arm in open communication with the upper end of an elongated cylindrical oven chamber of substantially uniform cross section, a third chamber of substantially greater cross section than said oven chamber in open communication with the lower end of said oven chamber and a spent sample collection chamber in open communication with the lower end of said third chamber, said oven chamber containing therein a crucible selected from the group consisting of thoria-coated tantalum and thoria-coated molybdenum, means for centering said crucible in said oven chamber, means cooperating with said sample arm for transferring samples from said arm to said crucible, induction heating means surrounding a portion of said oven chamber, means within said head chamber for holding said crucible within that portion of said oven chamber surrounded by said induction heating means and for moving said crucible to and from said third chamber, said third chamber being provided with means for tipping said crucible to cause the analyzed sample to drop therefrom into said spent sample collection chamber, pump means for evacuating the evolved hydrogen from said chambers into a gas collection system of known volume, Pirani gauge means for measuring the pressure of hydrogen in said gas collection system, and means for evacuating said gas collection system.

8. An apparatus for determining the quantity of hydrogen in metals and alloys selected from the group consisting of titanium, zirconium, uranium and alloys rich in these metals which during operation is closed to the atmosphere comprising a head chamber containing at least one sample arm in open communication with the upper end of an elongated cylindrical oven chamber of substantially uniform cross section, a third chamber of substantially greater cross section than said oven chamber in open communication with the lower end of said oven chamber, and a spent sample collection chamber in open communication with the lower end of said third chamber, said oven chamber containing therein a crucible selected from the group consisting of thoria-coated tantalum and thoria-coated molybdenum, means for centering said crucible in said oven chamber, means cooperating with said sample arm for transferring samples from said arm to said crucible, induction heating means surrounding a portion of said oven chamber, means within said head chamber for holding said crucible within that portion of said oven chamber surrounded by said induction heating means and for moving said crucible to and from said third chamber, said third chamber being provided with means for tripping said crucible to cause the analyzed sample to drop therefrom into said spent sample collection chamber, pump means for evacuating the evolved hydrogen from v 10 a said chambers into a gas collection system of known volume, Pirani gauge means for indicating pressure changes in said gas collection system, strip chart recorder means for graphically recording the pressure changes indicated by said Pirani gauge, and means for evacuating said gas collection system.

References Cited in the file of this patent UNITED STATES PATENTS 2,387,878 Brown Oct. 30, 1945 FOREIGN PATENTS 706,535 Great Britain Mar. 31, 1954

Claims

1. AN APPARATUS FOR DETERMINING THE QUANTIFY OF HYDROGEN IN METALS AND ALLOYS WHICH DURING OPERATION IS CLOSED TO THE ATMOSPHERE COMPRISING A HEAD CHAMBER CONTAININGAT LEAST ONE SAMPLE ARM IN OPEN COMMUNICATION WITH THE UPPER END OF AN OVEN CHAMBER, A THIRD CHAMBER OF SUBSTANTIALLY GREATER CROSS SECTION THAN SAID OVEN IN OPEN COMMUNICATION WITH THE LOWER END OF SAID OVEN, SAID OVEN CONTAINING THEREIN A CRUCILBE WHICH HAS A MELTING POINT ABOVE ABOUT 1500* C. AND WHICH WILL NEITHER FUSE NOR ALLOY WITH THE SAMPLE TO BE ANALYZED, MEANS COOPERATING WITH SAID SAMPLE ARM FOR TRANSFERRING SAMPLES FROM SAID ARM TO SAID CRUCIBLE, HEATING MEANS SURROUNDING A PORTION OF SAID OVEN, MEAN WITHIN SAID HEAD CHAMBER FOR HOLDING SAID CRUCIBLE WITHIN THAT PORTION OF SAID OVEN SURROUNDED BY SAID HEATING MEANS AND FOR MOVING SAID CRUCIBLE TO SAID FROM SAID THIRD CHAMBER, SAID THIRD CHAMBER BEING PROVIDED WITH MEANS FOR REMOVING THE ANALYZED SAMPLE FROM SAID CRUCIBLE TO THE BOTTOM OF SAID THIRD CHAMBER, PUMP MEANS FOR EVACUATING THE EVOLVED HYDROGEN FROM SAID CHAMBER INTO A GAS COLLECTION SYSTEM OF KNOWN VOLUME, MEANS FOR MEASURING THE PRESSURE OF HYDROGEN IN SAID GAS COLLECTION SYSTEM AND MEANS FOR EVACUATING SAID GAS COLLECTION SYSTEM.