US2708387A - Rapid spectroscopic determination of total water content - Google Patents

Rapid spectroscopic determination of total water content Download PDF

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US2708387A
US2708387A US384802A US38480253A US2708387A US 2708387 A US2708387 A US 2708387A US 384802 A US384802 A US 384802A US 38480253 A US38480253 A US 38480253A US 2708387 A US2708387 A US 2708387A
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water content
deuterium
oxide
total water
hydrogen
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Herbert P Broida
Harold J Morowitz
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/66—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence
    • G01N21/69—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light electrically excited, e.g. electroluminescence specially adapted for fluids, e.g. molten metal

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  • This invention concerns the problem of determining the total water content-water present in free, absorbed, hydrated, and/or bound form-of various materials. This is a problem of great commercial and practical importance. For instance, millions of bushels of corn and other cereal products are sold annually on terms that take moisture content into consideration. The textile and cement industries, among others, also have important problems of water content determination. But until now there has been no easy and rapid way of determining total water content.
  • the present invention provides a quick, simple method of determining with high precision the water content of practically any substance. A known amount of the substance is immersed in a mixture of hydrogen and deuterium oxides; rapid spectroscopic determination of the ratio of these two oxides in the solution gives a measure of the Water content of the substance.
  • the classic general method of determining water content is by weight loss. A sample is heated to a room temperature high enough to drive 01T the water and is kept there until itsweight levels off. But when this method is used to determine the water content of corn, for instance, a hundred hours or more may be required for a determination. Even then, the accuracy of the determination leaves much to be desired.
  • Accuracy to within 1/10 of one percent of the true water content can be obtained by the method of the present invention. This accuracy is obtained even when the water content is small. For example, if the water content is only one percent of the total weight of the substance, the determination will be accurate to one part in 100,000 of the total weight of the substance. Such a determination can be made in a total time of one hour or less. If this high a degree of accuracy is not required, a determination of 3 percent accuracy can be made in about 7 minutes.
  • the irst object of the present invention is to provide a rapid and accurate method for the determination of total water content of substances.
  • Another object is to provide a new, more convenient, more practical method for water-content determinations required in industry and commerce.
  • Another object is to provide new, more convenient, methods for tracer studies, using stable isotopes instead of radioactive isotopes.
  • the figure shows a preferred form of equipment for use in Water content determinations by the method of the invention.
  • a sample of the material to be investigated is mixed with a solvent consisting of deuterium oxide or, more conveniently, with a measured volume of deuterium-oxide-hydrogenoxide mixture containing about 99 percent of deuterium oxide.
  • the resulting solution contains water (hydrogen oxide) from the sample, and by comparing the D20 to H2O ratio of this resulting solution with the D20 to H2O ratio of the original solvent the water content of the sample can be readily calculated.
  • the fraction, f by weight ofthe sample which is water is given to a rst approximation by the relation l where V is the volume of the solvent in milliliters and M is the weight of the original sample in grams.
  • the approximation, which is good to about 4 parts in 1000, is introduced by assuming that the partial molar volumes of hydrogen oxide and deuterium oxide are the same, and that the density of water in the range of room temperature is 1,000.
  • R and r are obtained by means of the apparatus shown in the figure. Briefly, what this apparatus does is to ow vapor from a deuterium-oxidehydrogen-oxide mixture through an electrodeless discharge tube at reduced pressure. Light emitted by the vapor in this tube, when the vapor is excited by radio-frequency energy, is analyzed by means of a recording spectrometer.
  • the deuterium-oxide-hydrogen-oxide mixture 1 to be analyzed is placed in a ask 2 which can be quickly connected to, or removed from, the rest of the system by means of connector 3. Air is removed by means of a suitable vacuum pump 4. Vapor from ask 2 flows through capillary constriction 6, ow gage 15, electrodeless discharge tube 8, and capillary constriction 7, where it is exhausted by vacuum pump 5. Constrictions 6 and 7 serve to control the flow of vapor through tube 8 as Well as the pressure in tube 8. Pressure gage 10 indicates the pressure in tube 8. Fixed pressures in the range of 0.3 and 1.0 mm. of mercury have been found satisfactory.
  • the vapor in'tube 8 is excited by placing tube 8 in a field of radio-frequency energy generated by an R.-F. exciter 9. Tube 8 is provided with a water jacket 11 for cooling.
  • the analysis depends on the wave-length separation of the emission lines of hydrogen and deuterium due to the isotopic shift.
  • the ratio of hydrogen to deuterium can be determined by measuring the ratio of the Hg line (4861.3 A.) to the D, line (4860.0 A.) coming from the discharge. Vapor in the discharge dissociates into H and OH and D and OD, and the observed ratio of the intensity of the hydrogen to the deuterium line will be a measure of the ratio of hydrogen oxide to deuterium oxide. It has been established that the ratio of excited hydrogen to deuterium is proportional to the ratio of the concentration of hydrogen oxide vapor to deuterium oxide vapor.
  • light from tube 8 passes through condensing lens 12 and entrance slit 13A to spherical mirror 14.
  • Mirror 14 reflects the light to diffraction grating 16; a grating ruled 12,000 lines per centimeter has given satisfactory results.
  • Grating 16 is slowly rotated by motor 17, and suitable speed-rcduction gearing if needed.
  • Monochromatic light from grating 16 is reflected by mirror 14 to exit slit 1S.
  • Photomultiplier tube 19 responds to the monochromatic light passing through exit slit 18, The electrical output of photomultiplier tube 19 is amplified by directcurrent amplifier 21 and fed to strip-chart recorder 22.
  • deuterium oxide and spectroanalyzing the resulting solution to determine the relative proportions of deuterium oxide and hydrogen oxide present in said solution.
  • said spectro-analyzing comprises subjecting vapor from said solution, at reduced pressure, to radio-frequency excitation, said vapor being flowed continuously through the region in which it is subjected to said radio-frequency excitation; resolving the light emitted by said vapor when thus excited into monochromatic light; and measuring photoelectrically the intensities of at least one spectral line indicative of the presence of deuterium and at least one spectral line indicative of the presence of hydrogen.
  • the method of the invention does not depend on 0bservation of the HB and D@ spectral lines mentioned above. Any pair of spectral lines can be observed,

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Description

@mwa
May 17, 1955 H. P. BRolDA ETAL RAPID SPECTROSCOPIC DETERMINATION OF TOTAL WATER CONTENT Filed Oct. 7, 1953 wks.
INVENTOR Herber'zL P Broz'da Harold ./Morom'zz AGENT United States Patent O RAPID SPECTROSCOPIC DETERMINATION OF TOTAL WATER CONTENT Herbert P. Broida, Bethesda, and Harold J. Morowitz, Kensington, Md.
Application October 7, 1953, Serial No. 384,802
7 Claims. (Cl. 88-14) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment to me of any royalty thereon, in accordance with the provisions of 35 United States Code (1952), section 266.
This invention concerns the problem of determining the total water content-water present in free, absorbed, hydrated, and/or bound form-of various materials. This is a problem of great commercial and practical importance. For instance, millions of bushels of corn and other cereal products are sold annually on terms that take moisture content into consideration. The textile and cement industries, among others, also have important problems of water content determination. But until now there has been no easy and rapid way of determining total water content. The present invention provides a quick, simple method of determining with high precision the water content of practically any substance. A known amount of the substance is immersed in a mixture of hydrogen and deuterium oxides; rapid spectroscopic determination of the ratio of these two oxides in the solution gives a measure of the Water content of the substance.
The classic general method of determining water content is by weight loss. A sample is heated to a room temperature high enough to drive 01T the water and is kept there until itsweight levels off. But when this method is used to determine the water content of corn, for instance, a hundred hours or more may be required for a determination. Even then, the accuracy of the determination leaves much to be desired.
More recently, some determinations of Water content have been made by mixing the sample with heavy water and analyzing the resulting solution for deuterium-hydrogen ratio by means of a mass spectrometer. Although this method gives higher precision than the weight-loss method, it is still very slow and requires more elaborate equipment than the method of the present invention.
Accuracy to within 1/10 of one percent of the true water content can be obtained by the method of the present invention. This accuracy is obtained even when the water content is small. For example, if the water content is only one percent of the total weight of the substance, the determination will be accurate to one part in 100,000 of the total weight of the substance. Such a determination can be made in a total time of one hour or less. If this high a degree of accuracy is not required, a determination of 3 percent accuracy can be made in about 7 minutes.
The irst object of the present invention is to provide a rapid and accurate method for the determination of total water content of substances.
Another object is to provide a new, more convenient, more practical method for water-content determinations required in industry and commerce.
Another object is to provide new, more convenient, methods for tracer studies, using stable isotopes instead of radioactive isotopes.
Other uses and advantages of the invention will become 2,708,387 Patented May 17, 1955 apparent upon reference to the specification and drawing.
The figure shows a preferred form of equipment for use in Water content determinations by the method of the invention.
To make a Water content determination, a sample of the material to be investigated is mixed with a solvent consisting of deuterium oxide or, more conveniently, with a measured volume of deuterium-oxide-hydrogenoxide mixture containing about 99 percent of deuterium oxide. The resulting solution contains water (hydrogen oxide) from the sample, and by comparing the D20 to H2O ratio of this resulting solution with the D20 to H2O ratio of the original solvent the water content of the sample can be readily calculated. v
If the molar ratio of the hydrogen oxide to `deuterium oxide in the original solvent is r, and the iinal molar ratio of the solution is R, then the fraction, f by weight ofthe sample which is water is given to a rst approximation by the relation l where V is the volume of the solvent in milliliters and M is the weight of the original sample in grams. The approximation, which is good to about 4 parts in 1000, is introduced by assuming that the partial molar volumes of hydrogen oxide and deuterium oxide are the same, and that the density of water in the range of room temperature is 1,000.
The values of R and r are obtained by means of the apparatus shown in the figure. Briefly, what this apparatus does is to ow vapor from a deuterium-oxidehydrogen-oxide mixture through an electrodeless discharge tube at reduced pressure. Light emitted by the vapor in this tube, when the vapor is excited by radio-frequency energy, is analyzed by means of a recording spectrometer.
Referring to the drawing, the deuterium-oxide-hydrogen-oxide mixture 1 to be analyzed is placed in a ask 2 which can be quickly connected to, or removed from, the rest of the system by means of connector 3. Air is removed by means of a suitable vacuum pump 4. Vapor from ask 2 flows through capillary constriction 6, ow gage 15, electrodeless discharge tube 8, and capillary constriction 7, where it is exhausted by vacuum pump 5. Constrictions 6 and 7 serve to control the flow of vapor through tube 8 as Well as the pressure in tube 8. Pressure gage 10 indicates the pressure in tube 8. Fixed pressures in the range of 0.3 and 1.0 mm. of mercury have been found satisfactory. The vapor in'tube 8 is excited by placing tube 8 in a field of radio-frequency energy generated by an R.-F. exciter 9. Tube 8 is provided with a water jacket 11 for cooling.
It is important for accuracy that the vapor in the discharge tube ilow continuously during the analysis, so that only fresh vaporis analyzed atall times. If the vapor in the tube is closed oi, the percentage of deuterium tends to change with time.
The analysis depends on the wave-length separation of the emission lines of hydrogen and deuterium due to the isotopic shift. The ratio of hydrogen to deuterium can be determined by measuring the ratio of the Hg line (4861.3 A.) to the D, line (4860.0 A.) coming from the discharge. Vapor in the discharge dissociates into H and OH and D and OD, and the observed ratio of the intensity of the hydrogen to the deuterium line will be a measure of the ratio of hydrogen oxide to deuterium oxide. It has been established that the ratio of excited hydrogen to deuterium is proportional to the ratio of the concentration of hydrogen oxide vapor to deuterium oxide vapor.
Still referring to the drawing, light from tube 8 passes through condensing lens 12 and entrance slit 13A to spherical mirror 14. Mirror 14 reflects the light to diffraction grating 16; a grating ruled 12,000 lines per centimeter has given satisfactory results. Grating 16 is slowly rotated by motor 17, and suitable speed-rcduction gearing if needed. Monochromatic light from grating 16 is reflected by mirror 14 to exit slit 1S. Photomultiplier tube 19 responds to the monochromatic light passing through exit slit 18, The electrical output of photomultiplier tube 19 is amplified by directcurrent amplifier 21 and fed to strip-chart recorder 22.
With this arrangement, by rotating grating 16 to scan the desired portion of the spectrum, a graphic recording showing the amplitudes of the Hp and D lines can be obtained in about 20 seconds.
In the table below are given experimental results obtained with the method of the present invention when analyzing three different samples. It can be seen from this table that the experimental and theoretical results are in close agreement. Therefore the present invention provides a highly accurate as Well as a very rapid method for determining the total water content of bodies.
deuterium oxide and spectroanalyzing the resulting solution to determine the relative proportions of deuterium oxide and hydrogen oxide present in said solution.
2. The invention according to claim 1 in which said solvent comprises a mixture of deuterium oxide and hydrogen oxide. Y
3. The invention according to claim 1 in which said solvent comprises a mixture of deuterium oxide and hydrogen oxide in known proportions, at least 50 percent by weight of said mixture being deuterium oxide.
4. The invention according to claim l in which said spectro-analyzing comprises subjecting vapor from said solution, at reduced pressure, to radio-frequency excitation, said vapor being flowed continuously through the region in which it is subjected to said radio-frequency excitation; resolving the light emitted by said vapor when thus excited into monochromatic light; and measuring photoelectrically the intensities of at least one spectral line indicative of the presence of deuterium and at least one spectral line indicative of the presence of hydrogen.
5. The invention according to claim 4, said reduced Experimental determination of total hydration Experimental Solvent Solutlon Hydration Hydrate Solvent, Ratio Hy- Ratlo Hy- Material gram m1. drogen to drogen to Egg stu' 'lhmlcal (M) (V) Deuterium Deuterium ar f ls/Ivla lon y ra on (r) 11) ea CLISO4.5H2O 0. 770 1. O0 0. 011 0. 286 0. 354;l;0A 003 0. 361 NazSzOLSHnO. 0. 648 1. 00 011 0. 249 0. 34zh0. O03 0. 363 NEQSQO3.5H2O 0. 779 1. 00 0. 011 0. 289 0. 353:l:0. 003 0. 363
The method of the invention does not depend on 0bservation of the HB and D@ spectral lines mentioned above. Any pair of spectral lines can be observed,
provided that one of them is characteristic of deuterium and the other of hydrogen. The lines observed may be characteristic of molecules, including D20 and H2O, as well as of atoms. Other spectro-analytic means than those described can be used.
What is claimed is:
1. The method of determining the total water content of a substance the steps of which comprise mixing a sample of the substance with a solvent containing No references cited.

Claims (1)

1. THE METHOD OF DETERMINING THE TOTAL WATER CONTENT OF A SUBSTANCE THE STEPS OF WHICH COMPRISE MIXING A SAMPLE OF THE SUBSTANCE WITH A SOLVENT CONTAINING DEUTERIUM OXIDE AND SPECTROANALYZING THE RESULTING SO-
US384802A 1953-10-07 1953-10-07 Rapid spectroscopic determination of total water content Expired - Lifetime US2708387A (en)

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2908819A (en) * 1955-06-13 1959-10-13 Phillips Petroleum Co Apparatus for measuring properties of gases
US2967451A (en) * 1957-04-04 1961-01-10 Waters Corp Method and apparatus for gas analysis
US2975669A (en) * 1954-08-26 1961-03-21 Jarrell Ash Company Crossed dispersion photographic spectrometer
US2991684A (en) * 1955-08-02 1961-07-11 Max Planck Inst Eisenforschung Method of supervising metallurgical and metal melting processes
US3242798A (en) * 1962-01-13 1966-03-29 Hitachi Ltd Plasma light source for spectroscopic analysis
US3309524A (en) * 1963-03-18 1967-03-14 Prengle Dukler & Crump Inc Hydrogen detector using hydrogen permeable membrane with feedbacks
US3424533A (en) * 1963-02-28 1969-01-28 Philips Corp Spectrographic analysis
US3455243A (en) * 1955-10-04 1969-07-15 Alphonse Martin Optical distance detecting devices
US3677642A (en) * 1967-08-04 1972-07-18 Varian Associates Ion cyclotron resonance stimulated glow-discharge method and apparatus for spectral analysis
US3727049A (en) * 1967-05-01 1973-04-10 Us Navy Method for determining immiscible water content of fluids by spectrophotometer
US5505829A (en) * 1993-01-06 1996-04-09 Villa-Aleman; Eliel Molecular separation method and apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975669A (en) * 1954-08-26 1961-03-21 Jarrell Ash Company Crossed dispersion photographic spectrometer
US2908819A (en) * 1955-06-13 1959-10-13 Phillips Petroleum Co Apparatus for measuring properties of gases
US2991684A (en) * 1955-08-02 1961-07-11 Max Planck Inst Eisenforschung Method of supervising metallurgical and metal melting processes
US3455243A (en) * 1955-10-04 1969-07-15 Alphonse Martin Optical distance detecting devices
US2967451A (en) * 1957-04-04 1961-01-10 Waters Corp Method and apparatus for gas analysis
US3242798A (en) * 1962-01-13 1966-03-29 Hitachi Ltd Plasma light source for spectroscopic analysis
US3424533A (en) * 1963-02-28 1969-01-28 Philips Corp Spectrographic analysis
US3309524A (en) * 1963-03-18 1967-03-14 Prengle Dukler & Crump Inc Hydrogen detector using hydrogen permeable membrane with feedbacks
US3727049A (en) * 1967-05-01 1973-04-10 Us Navy Method for determining immiscible water content of fluids by spectrophotometer
US3677642A (en) * 1967-08-04 1972-07-18 Varian Associates Ion cyclotron resonance stimulated glow-discharge method and apparatus for spectral analysis
US5505829A (en) * 1993-01-06 1996-04-09 Villa-Aleman; Eliel Molecular separation method and apparatus

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