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Vol. 16. No. 2
The Accurate Determination of Nitrates in Soils’” Phenoldisulfonic Acid Method By Horace J. Harper UNIVERSITY OF WISCONSIN, MADISON,WrS.
F THEmethods de-
tions as the copper, iron, and aluminium salts, except on two sandy soils. Calcium carbonate was by far the poorest flocculent. This and further experiments indicated that inorganic colloids can be removed satisfactorily from soil extracts by several of the different flocculents. However, when two peats and an acid black soil were used, colorless solutions could not be obtained by the use of these flocculents, owing to the presence of organic cploring matter which they would not remove. The filtrates, when evaporated, gave residues containing appreciable amounts of organic matter. Emersonll uses alumina cream to remove coloring matter from soil extracts. Schreiner and Failyer12 recommend “G Elf” carbon black for this purpose. A comparison was made of the clarifying power of three different charcoals and the hydroxides of copper, iron, aluminium, zinc, and manganese. A 0.2 per cent caramel solution similar to that employed by Emersonll was used in this experiment. The charcoal was added a t the rate of 1 gram to 100 cc. of the solution. Five cubic centimeters of a normal solution of copper, ferric, aluminium, zinc, and manganese sulfates were added separately to 100-cc. portions of the caramel solution, and 0.25 gram of calcium hydroxide was added to precipitate the hydroxides of the metals. The solutions were shaken for 20 minutes, filtered, and the filtrates compared. The results are given in Table I.
A simple analytical procedure has been developed for the accurate
s ~ r i b e d ~ ~for * ~the ~ ~ * ~determination * of nitrate by the phenoldisulfonic acid method. Perdetermination of nifectly clear and colorless soil extracts are obtained by the use of a cop%rates in soils, the phenolper sulfate and a copper hydroxide treatment. disulfonic acid method is I t has been found by other investigators that losses of nitrate occur the most frequently used due to the evaporation of acidfilfrates,the use of various decolorizing because of its simplicity and agents, the presence of chlorides above 15 parts per million in the rapidity. Objections to this soil, and the presence of carbonates in the residue to which the phemethod have been made noldisulfonic acid is added. Loss of nitrate in these ways can be owing to the difficulty of prevented by keeping the solution alkaline on evaporation, by using obtaining accurate results, copper hydroxide as a decolorizing agent, by removing the chlorides for one or more of the followwith silver sulfate, and by flooding the dry residues with 3 cc. of ing reasons: (1) difficulty in phenoldisulfonic acid. obtaining a perfectly clear Interfering tints that occur in making comparisons between standand colorless extract, which ard and unknown solufions are caused by the presence of organic is absolutely essential; (2) coloring matter, irregularities in adding the different reagents, and the losses of nitrates during depresence of insoluble material in the unknown solution. These tints termination due to several can be prevented by removing the organic matter with copper hyspecific causes; (3) difficulty droxide, by treating all residues uniformly as directed, and by fib in making accurate comtering to remooe material not in solution. parisons between standard I f the procedure as outlined is carefully followed, w r y accurate and unknown solutions due results may be obtained. to interfering tints. CLARIFYING AND DECOLORIZING THE SOILEXTRACT An absolutely clear and colorless extract must be obtained in order to secure accurate results with this method. PasteurChamberland filters are sometimes used to clarify soil extracts, but they do not remove color due to organic matter. Their use requires more apparatus and time than is desirable, and hence numerous flocculating agents have been used, making it possible to use paper filters. The different flocculating agents recommended for clarification are calcium oxide, calcium hydrate,6 calcium carbonate,’ copper s ~ l f a t e ,and ~ potash alum.* A comparison of these flocculents apd also ferric and aluminium sulfate was made, using twelve soils having widely different physical and chemical properties ranging from sand to clay loam, from low organic matter content to raw peat, and from very acid to alkaline in reaction. Each of the flocculents recommended by the previous investigators was added to 50 grams of soil and 260 cc. of distilled water. The iron and aluminium sulfates were added at the rate of 1 gram to 100 grams of soil. The suspensions were shaken for 30 minutes and filtered, using ordinary filter paper (5. & S. 597). Seventy-five cubic centimeters of each of the filtrates were compared in Nessler tubes, and 25 cc. were evaporated to dryness and comparisons made between different residues. There was very little difference in color between the filtrates or dry residues from the copper sulfate, ferric sulfate, aluminium sulfate, and potash alum treatments. I n the case of peats, calcium oxide and calcium hydrate increased the color of the extracts over that of pure water extracts, and did not give such clear and colorless soluReceived July 2, 1923. Part I of a thesis submitted at the University of Wisconsin in partial fulfilment of the requirements for the degree of doctor of philosophy. Published with the permission of the Director of the Wisconsin Agricultural Experiment Station. Numbers in text refer to bibliography at end of article. 1
a
*
TABLEI-EFF~CTOF DIFFERENT D E C O L O R ~ ZAGENTS ~ N G O N A 0.2 PER CENT CARAMEL SOLUTION Order of EEciency CLARIFYING AGENT in Removing Color COLOROF FILTRATES Charcoal (animal) 1 No color Carbon black (“GElf”) 2 Cu (0H)n 3 Slight color 4 Fe(0H)r AI(OH~ 6 Considerable color Mn(0H)n Zn(0H)r (blood) Charcoal
78
Little change
This experiment was repeated using an alkaline peat extract, an acid peat extract, and two alkaline extracts secured from a manure compost heap. All the extracts except the alkaline peat were darker in color than a 1 per cent caramel solution. The same relative results were obtained as given in Table I. The animal charcoal and “G Elf” carbon black were the best decolorizing agents, copper and ferric hydroxide were superior to alumina cream, while the blood charcoal was least effective in removing the color from the different solutions. The “G Elf” carbon black filtrates, although they always appeared very clear, on evaporation contained
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
a black residue due to finely divided carbon passing through the filter. This was prevented by precipitating copper hydroxide in the solution treated with carbon black before filtering. Since charcoal cannot flocculate soil suspensions, may adsorb more or less nitrate, and is difficult to wash from apparatus, itii general use as a decolorizing agent is not recommended. However, in the case of very highly colored soil extracts, which are occasionally obtained and cannot be decolorized, even with larger amounts of copper hydroxide, “G Elf” carbon black may be used along with the copper sulfate-copper hydroxide treatment recommended under analytical procedure. This combination will decolorize very highly colored solutions with only a slight loss of nitrate.
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that the sulfuric acid, having a higher boiling point than nitric acid, displaces the nitric acid from its salts a t the temperature of the steam bath and causes it to be volatilized as the residues approach dryness. This loss can always be prevented by neutralizing the filtrate before evaporation, preferably with a saturated calcium hydroxide solution. Loss DUE TO CARBONATES-Aserious loss due to carbonates occurs when the phenoldisulfonic acid is added to dry residues containing considerable carbonates. If calcium oxide or calcium hydrate has been used as a soil flocculent, if acid extracts were neutralized before evaporation, or if carbonates were naturally present in the soil, some carbonate will be present in the residue after evaporation. If the phenoldisulfonic acid is added slowly in a ring around the edge of the residue,6 each drop will move slowly toward the center NITRATELOSSES of the dish. The reaction between the sulfuric acid in the Loss DUE TO ADSORPTION-Emerson,ll Iipman and reagent and the salts in the residue results in the liberation Sharp,5 and others have shown that some charcoals adsorb of free nitric and carbonic acids. The carbonic acid gas nitrates. I n this investigation it was found that animal passes off around the edges of each drop of reagent and charcoal adsorbs large amounts of nitrate while the “G Elf” mechanically helps to carry some nitric acid away with it carbon black removes very little. I n each case 10 parts before the nitric acid has a chance to react with the phenoldiper million of nitrogen as nitrate were added t o the solution sulfonic acid. Daviss recommends flooding the residues with and the charcoal suspension was shaken 20 minutes before 5 cc. of reagent in order to prevent this loss. filtering. The results are given in Table 11. Since nitrates are more soluble than the other salts present, on evaporation they are concentrated in the lowest TABLE 11-Loss OF NITRATE WHEN DIRFERBNT CHARCOALS ARB USEDAS DECOLORIZING AGENTSON A SOLUTION CONTAININQ 10 P. P. M. OF NITRO- part of the evaporating dish. I n order to prevent loss of GEN A S NITRATE nitrate due to carbonates, 3 cc. of reagent are added quickly NITROGEN AS NITRATE DECOLURIZINQ AGENT Grams in Recovered Lost to the center of the evaporating dish. The carbon dioxide 250 Cc. P. p. m. P.p. m. which is evolved must pass upward through the reagent, Animal charcoal 0.5 8.6 1.4 1 7.7 2.3 and any nitric acid which might be carried awaywith it also has 2 6.6 3.4 to pass up through the reagent and thue reacts with the phenol“G Elf” carbon black 0.5 9.7 0.3 2 9.6 0.5 disulfonic acid, and loss of nitrate is prevented. I n case of Lipman and Sharp6 have also reported a loss of nitrate alkali soils containing large quantities of soluble carbonates, when alumina cream was used to clarify the soil extract. the solution should be almost neutralized with dilute sulfurio Tests were made to determine the effect of copper, aluminium, acid before evaporation, as recommended by Chamot, Pratt, and ferric hydroxides on the adsorption of nitrate. The and Redfield.13 LOSS DUE TO CHLORIDES-stewart and Greaves,14 Davis,E amount of hydroxide used was equivalent to 5 cc. of a normal solution. It was precipitated from a sulfate solutJionby add- and others have shown that chlorides cause a loss of nitrate. ing 0.25 gram of calcium hydroxide. The total volume was Lombard and Laforel5 have shown that the loss was due to 250 co. No adsorption of nitrate by any of the hydroxides the formation of aqua regia when the phenoldisulfonic acid used could be detected in a solution containing 10 parts per was added to a dry mixture of chloride and nitrate. Pougetle and others recommend the removal of the chlorides by the million of nitrogen as nitrate. Another experiment was conducted on a silt loam soil re- use of silver sulfate in order to prevent loss of nitrate. A test was made of the effect of chlorides on the loss of niceiving 24 tons of manure annually. The sample was taken in November and the nitrate content was low. Fifty grams trate by adding a solution of potassium nitrate containing of soil were shaken up with 250 cc. of solution containing the 10 parts per million of nitrogen as nitrate and varying amounts of chloride to a nitrate-free black clay loam. The results flocculating agent. It was found that large increases in amount of copper hy- were similar to those secured by Stewart and Greavesx4and droxide caused only a slight increase in adsorption of nitrates. Lipman and Sharp,E which indicate that there is loss of From this it may be inferred that adsorption of nitrates by the nitrate when the chloride content exceeds 4 parts per million in the solution evaporated, which is equivalent to 20 parts amount of copper hydroxide required is negligible. Loss MJRIKG EVAPORATION-se~ei”al investigators have per million of chloride in the dry soil. In another experiment it was found that complete recovery reported loss of nitrate when potash alum was used as a soil flocculent. Dilute solutions of potash alum, aluminium of nitrates was obtained when a solution of silver sulfate was sulfate, and ferric sulfate have an acidity greater than pH =4. added as recommended in the analytical procedure. An excess of 100 parts per million of silver is necessary to Unless soils are alkaline in reaction these salts will produce acid filtrates. Davis,8 using potash alum as a flocculating insure complete removal of chloride from the soil extracts agent, added 10 to 15 cc. of a saturated solution of calcium when the chloride content is very high. The amount of chlohydroxide to the aliquots before evaporation and prevented ride in an unknown sample of soil can be quickly determinedl2 loss of nitrate. His results have been confirmed in this by titrating a portion of the filtrate with standard silver niinvestigation. Chamot, Pratt, and RedfieldlS recommend trate solution using potassium chromate as an indicator. I n that acid waters be neutralized before evaporation to prevent case of pot tests or in field studies where fertilizers containing chlorides have been added to the soil, the amount of silver loss of nitrate. The loss of nitrate which has often been attributed to the necessary to remove the chloride can be quickly calculated presence of sulfates in solution is not due to the sulfate, but and the proper amount of silver sulfate solution can be added is governed by the reaction of the evaporating solution. with the water and copper sulfate solution. Daviss reports that nitrate can be completely recovered in No loss of nitrate occurs if it is alkaline. If it is acid, the loss of nitrate is proportional to the acidity, owing t o the fact the presence of chlorides by flooding the dry residues with 12
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cc. of phenoldisulfonic acid. It is usually better to remove the chloride with silver sulfate than to use such a large quantity of reagent, which is very apt to cause color tints.l8 Moreover, a very large volume of liquid is obtained on dilution and neutralization, which prevents accurate comparison with the standard when the nitrate content is low. ELIMINATION OF COLOR TINTS The presence of color tints in the unknown nitrate solution prevents an accurate comparison with the standard. These tints are due mainly to three factors: (1) organic matter in the residues; (2) salts not in solution; and (3) irregularities in adding phenoldisulfonic acid, subsequent dilution, and neutralization. When copper hydroxide is used as a decolorizing agent, organic matter should not be a factor in causing color tints. If the phenoldisulfonic acid is neutralized before all the residue is dissolved, it will be necessary to filter the solution and remove the insoluble salts in order to make an accurate comparison of the unknown and standard. If they are not removed these salts will cause a refraction of the light rays, and color tints will be produced. This can easily be demonstrated by adding a little calcium sulfate to a portion of a standard solution and comparing it with some of the regular untreated standard. The errors resulting from irregularity in adding different reagents can only be eliminated by accurately following the directions given in the analytical procedure. COMPLETENESS OF EXTRACTION OF NITRATEFROM SOILS WITH THE PROCEDURE LATERRECOMMENDED Allen and Bonazzi18 report that only 77.4 per cent of the total nitrate (average for ten soils) was secured in the first extraction. Potter and Snyder7JS report that 93 to 97 per cent of the nitrate added to a soil was recovered by the phenoldisulfonic acid method and that complete recovery of nitrate was obtained by the reduction method when a known amount of nitrate was added to a soil which had previously been analyzed for nitrates. Kelley and Brownz0 find that approximately as much nitrate is extracted from alkali soils in 5 minutes as’in 8 hours, and that further extraction does not yield appreciable amounts of nitrate. Similar results were secured in this investigation. Noyes6 reports that nitrates added to a soil, in addition to those already present, can be completely recovered in one extraction with water. I n the following experiments seven soils which possessed very different properties were washed free of nitrates and dried in a steam oven at 55” C. None of them gave a test for nitrate when a 25-cc. aliquot from a 1: 5 extract was evaporated and treated in the usual manner for nitrates. A known amount of nitrate was added and the amount recovered was determined by the analytical procedure recommended. The results of this experiment are given in Table 111. TABLE111-RECOV~RY OF NITRATB FROM
-
SOIL CONTAINING
OUANTITKES OR NITRATE
SOIL Black
clay
REACTION loam
(Texas) .......... Neutral Carrington loam. , Acid Kewaunee loam., Very acid
.. ... Miami silt loam., ... Plainfield sand. ..... Raw Peat
peat.. .........
...............
KNOWN
P. P. M. NITROGEN AS NITRATE RECOVRRBD
Neutral Acid Very acid Alkaline
10P.p.m. Added
25P.p.m. Added
10.00 9.85 9.85 9.30 10.00 9.86 9.85
24.70 24.20 25.15 23.70 24.82 24.30 25.15
100P.p.m. Added
... ioi:4
97.2
...
97.2 100.0
The recovery of nitrate in the foregoing experiment is undoubtedly as accurate as could be obtained by any other method. Complete recovery of nitrate was not always obtained, but the amounts not recovered were very small and negligible for most purposes. The largest loss was with the Miami silt loam, and shaking for an hour did not give any
Vol. 16, No. 2
better results than shaking 15 minutes. This soil contains a very high percentage of colloidal material and i t is possible that the nitrate which was not recovered was held by adsorption. Gustafson21 and also KingZ2report that some nitrate is firmly held by the force of adhesion in the surface film of water surrounding the soil particles, and that one extraction will not remove this nitrate. This same slight error due t o adsorption of nitrates occurs also with any other method. When calcium carbonate was used as a flocculent as recommended by Potter and Snyder,? or calcium hydroxide as recommended by Noyes,e it was impossible to determine the nitrate content of the two peat soils owing to the large amount of organic matter in the extract. RECOMMENDED ANALYTICAL PROCEDURE Pulverize and mix the soil thoroughly by passing it through an 8-mesh sieve. I n the case of heavy soils which contain considerable amounts of small, hard granules, due to intense drying, it is advisable to grind the soil so that it will pass a 60-mesh sieve in order to facilitate complete wetting in the time allowed. Weigh out 50 grams of soil (25 grams in case of peat) and place it in a 500-cc., wide-mouth bottle. Add 250 cc. of distilled water containing 5 cc. of a normal ,copper sulfate solution and shake 10 minutes. If the soil is not very acid and does not give a colored extract, add 0.4 gram of calcium hydroxide and 1 gram of magnesium carbonate to the soil suspension and shake 5 minutes more to precipitate the.copper. Filter on a dry filter and discard the first 20 cc. of liltrate. If the soil is very acid or gives a colored extract, allow to settle after the first shaking of 10 minutes, and decant about 125 cc. of the supernatant liquid into a flask. Add to this flask 0.2 gram of calcium hydroxide and 0.5 gram of magnesium carbonate, shake 5 minutes, and filter as before. I n either case transfer 10-cc. portions (use 25 cc. or more if the nitrate content is less than 10 parts per million) with a pipet to 7.6 cm. (3-inch) evaporating dishes. Evaporate aliquots to dryness on a steam bath. Cool the dishes, add rapidly 2 cc. of phenoldisulfonic acid from a pipet or buret having the tip cut off directly to the center of each evaporating dish, and then rotate the dish in such a way that the reagent comes in contact with all the residue. Let the reagent act 10 minutes, then add 15 cc. of cold water and stir with a short glass rod until residue is insolution. When cool, slowly add dilute ammonium hydroxide (1 volume NHdOH, specific gravity 0.90, to 2 volumes of water) till slightly alkaline. Transfer solution to a cylinder or Nessler tube, dilute, and compare with standard solution containing 1 part per million of nitrogen as nitrate. If the soil contains more than 15 parts per million of chloride, which is seldom the case in soils of the humid region, the chloride is removed by including a solution of silver sulfate (4 grams in 1000 cc.) in the 250 cc. of solution with which the soil is treated. Ten cubic centimeters of this solution are sufficient to remove completely 80 parts per million of chloride calculated on the basis of dry soil. After shaking 10 minutes, decant off 125 cc. as in case of colored extracts or very acid soils, add 0.2 gram of calcium hydroxide and 0.5 gram magnesium carbonate to precipitate the silver and copper, shake 5 minutes, filter, and proceed as described above. I n case the chloride content is very high, add solid silver sulfate to the soil suspension before shaking. I n case of highly colored soil extracts that rarely cannot be decolorized by the copper sulfate-copper hydroxide treatment, add 1 gram of “G Elf” carbon black to 100 cc. of the supernatant liquid secured as recommended for colored extracts, and shake 15 or 20 minutes before adding the calcium hydroxide and magnesium carbonate to the solution. If the soil is calcareous, an additional 5 cc. of 1 N copper sulfate should be added to the soil extract with the carbon black to
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INDUSTRIAL AND ENGINEERING CHEMISTRY
insure enough copper hydroxide to completely remove the colloidal carbon on filtration.
DISCUSSION OF THE ANALYTICAL PROCEDURE This procedure is similar to that of Beak4 in that copper sulfate and hydroxide are used for clarifying and decolorizing the soil extract. The writer found that the copper, as copper hydroxide, could be more advantageously precipitated with calcium hydroxide in the cold than with magnesium oxide and heating, and that this precipitation in most cases could be accomplished in the soil suspension. Magnesium carbonate is added to remove the excess of calcium hydroxide. This procedcire is simple and rapid and an alkaline extract is also obtained which prevents loss of nitrate, as shown by Davis,8 who used potash alum as a flocculent. It was found that flooding the residue with an excess of phenoldisulfonic acid as recommended by Davis8 is necessary to prevent loss of nitrate when considerable carbonates are present,. The reason for this has been explained. The use of copper sulfate and its removal as outlined in placeof potash alum gives a solytion which is seldom acid to phenolphthalein and contains much smaller amounts of soluble salts. The residue is thus smaller, contains less carbonates, and hence a less amount of phenoldisulfonic acid$ necessary for flooding than that recommended by Davis.8 The writer has found ammonium hydroxide preferable to Dotassium hvdroxide for the neutralization of the Dhenoldiklfonio acid: The use of potassium hydroxide gives rise to often than the use of insoluble precipitates much ammonium hydroxide. The ammonium hydroxide is also a much more convenient laboratory reagent. The us8 of properly prepared phenoldisulfonic acid is important). This reagent is prepared according to Chamot, Pratt, end Redfield,l7 as follows: Dissolve 25 grams of pure phenol in 150 cc. of concentrated sulfuric acid. Add 75 cc.
183
of fuming sulfuric acid, mix, and heat in a flask by placing the flask in boiling water for 2 hours. Store in a brawn bottle. The standard nitrate solution was made according to directions given by Bear and Salter.4 The analytical procedure given embodies the best points of several methods with certain modifications of the miter.
ACKNOWLEDGMENT The writer wishes to express his appreciation of the suggestions and criticisms offered by Professor E. Truog in connection with this study. BIBLIOGRAPHY I-Tieman-Gartner, “Handbuch der Untersuchen und Beurteilung der Wasser,” 4th edition, 1895. 2-U. S. Dept. Agr., Bur. Chem., Bull. 107. 3--Whiting, Richmond and Schoonover. J . I n d . Eng. Chem., 12, 982 (1920). 4-Bear and Salter, W. Va. Agr. Expt. Sta., Bull. 159,23 (1916). 5-Lipman and Sharp, U n i v , Cali,?.Publications i n Agricultural Science, 1, 21 (1912). 6--Noyes, J . I n d . Eng. Chem., 11, 213 (1919) 7-Potter and Snyder, I b i d . , 7, 863 (1915). 8-Davis, Ibid., 9, 290 (1917). 9-Comber, J . Agr. Sci., 11,450 (1921). 10-Wolkoff, Soil Science, 1, 585 (1916). 11-Emerson, l b i d . , 12, 413 (1921). 12-Schreiner and Failyer, U.S. Dept. Agr., Bur. Soils, Bull. 31. l3-Chamot, Pratt and Redfield, J . A m . Chem. SOC.,33, 366 (1911). 14-Stewart and Greaves,lbzd., 32, 756 (1910); 36,579 (1913). 15-Lombard and Lafore, Bull. SOC. chim.. 6, 321 (1909). 16--Pouget, Ibid., 7, 449 (1910). 17-Chamot, P r a t t , and Redfield, J . Am. Chem. SOC.,38, 381 (1911). 18-Allen and Bonazzi, Ohio Agr. Expt. Sta., Tech. Series, Bull. 7 (1915). 19-Potter and Snyder, J . Am. Soc. Agron., 8, 54 (1916). BO-Kelley and Brown, S o i l Science, 12, 261 (1921). 21-Gustafson, I b z d . , lS, 173 (1922). Trans. Wisconsin Acad. S C L ,16, 275 (1908); abitracted in 22-King, ~ ~ psta. t .Record, 21, 19 (1909).
Erskine Douglas Williamson T H E death of Erskine Douglas Williamson on December 25, group which went out into the factories and supervised the 1923, several days after an operation from which he seemed manufacture of optical glass for military needs. His particular to be recovering, was a sudden blow to his friends and colleagues field was the annealing of glass, and investigations begun while he was a t the glass plant were completed later a t at the Geophysical Laboratory. Born in Edinthe Geophysical Laboratory. For his share in burgh, Scotland, on April 10, 1886, he was only this investigation the Franklin Institute awarded thirty-seven a t the time of his death. him in 1921 the Edward Longstreth Medal of Mr. Williamson obtained his early education Merit. Another wartime activity in which he at George Watson’s College in Edinburgh, where took part was the determination of the compressihe showed marked ability in science and mathebility of mustard gas. Since the close of the war matics. He graduated with high honors from he has been engaged in the investigation of several the University of Edinburgh, receiving the degrees phases of the behavior of materials under very of B.Sc in 1908 and M.A. in 1909. During the high pressures, particularly the compressibility of two years 1910 to 1912 he was science master in solutions and of minerals and rocks, the transGalashiels Academy, which he left to take up remission of earthquake waves, and the bearing search work in physical chemistry a t the Uniof these on the constitution of the interior of the versity of Edinburgh. While here he was granted earth. His latest activity was the construction a Carnegie scholarship, and in 1914 he went to of an apparatus for the determination of gravity. America to take a position on the scientific staff This work was unfinished a t the time of his death. of the Geophysical Laboratory of the Carnegie CHEMMr. Williamson joined the AMERICAN Institution of Washington. ICAL SOCIETY soon after coming t o this country By training a mathematician as well as a physand contirued to be an active member during the ical chemist, Mr. Williamson was able t o bring ensuing nine years. He was also a member of the this happy combination of faculties t o bear upon problems in many fields of scientific endeavor. AlEdinburgh Mathematical Society, a fellow of the E. D WILLIAMSON American Physical Society, a member of the Geothough well versed in chemistry and in physics, he had that mathematical temperament which allowed him t o deal logical Society of Washington, and of the Washington Academy of Sciences, and one of the editors of the Academy’s journal. with the purely abstract side of a problem, and to reachits solution With the passing of Mr. Williamson a very real loss is suffered with an apparent ease and with an elegance which was always a by his colleagues. A brilliant scholar and a quick thinker, he source of wonder to his colleagues. His first published researches possessed the unusual faculty of applying his attainments t o the dealt with the solubility relations of the various forms of calcium solution of problems which required the cooperative effort of and magnesium carbonates. Later he became interested in the several investigators. His thorough knowledge of a wide range thermodynamics of solutions as applied t o equilibria in solutions, particularly a t high pressures, and was one of that unfortunately of subjects made collaboration with him both pleasant and rather small circle which understands and appreciates the work profitable, and his generous nature endeared him to all his asI,. H. ADAMS of Willard Gibbs. During the war he wasa member of a sociates.
