July, 1924
I N D UXTRIAL A N D ENGINEERING CHEMISTRY
725
Determination of Anhydrous Soap in a Lubricating Grease' By Benjamin Joachim 745
EAST17.71% ST., BRONX, N. Y.
HE purpose of this article is to show wherein the long and tedious tentative method of the A. S. T. M.2 can be considerably shortened and a t the same time be made more accurate. OF FREE FATTY ACID DETERMIPV'ATION
T
For an accurate determination of the soap, the free fatty acid must first be determined. Weigh out a 10-gram sample in a 300-cc. Erlenmeyer flask, add a mixture (neutral to phenolphthalein) of 10 cc. 95 per cent, or stronger, alcohol and 90 cc. benzene, or, in case the oil is to be extracted for physical tests, naphtha, all of which shall distil below 76" c. Reflux until the grease is dissolved. In case of soda greases, the amount of alcohol can be increased. Filter hot, with suction, through a weighed Gooch. Wash the latter with hot, neutral benzene. The insoluble matter in the Gooch consists of filler, grit, and free insoluble oxide or carbonatei. e., CaO, CaC03, etc. Add sufficient water to the filtrate to make it 65 per cent alcoholic, or, where only 10 cc. alcohol had been used, add 25 cc. neutralized 50 per cent alcohol. Titrate for free acid, if present, with 0.1 N sodium hydrate, using phenolphthalein as indicator. This free acid titration we shall designate as A cc. 0.1 N sodium hydroxide per gram of grease. DETERMINATION OF FATTY ACIDFROM
THE
SOAP
As in the A. S. T. M. methods, two procedures are available-the bisulfate and the acid methods of liberating the fatty acids. I n the acid method we continue with the foregoiag procedure after titration of the free acid and add a large excess of (1:3) hydrochloric acid and reflux until the oil method I. should be layer is clear. For details, the A. S. T. & consulttbd. The objection to this method is essentially in the length of time of refluxing, besides the great difficulties from emulsions encountered later in the washing of the oily (naphtha) layer free from acid. This is especially true of high viscosity oils in the greases. In the bisulfate procedure, which is much quicker and more accurate, weigh out 5 to 10 grams of grease in a 50-cc. beaker provided with a small stirring rod, add 2 grams of finely powdered potassium bisulfate and place over direct steam for 10 to 20 minutes, stirring vigorously. Add 1 gram more of the bisulfate and stir on the steam bath for 5 minutes longer. Remove from steam bath, cool slightly, and add benzene or naphtha. Filter into an Erlenmeyer flask through a cotton plug placed loosely in a funnel and previously soaked in naphtha. In two years' experience, the author has never known any bisulfate to pass through. As an additional precaution, however, the filtrate may be washed with witter and the water layer tested for acid or sulfate. Add to the filtrate 60 cc. neutral 95 per cent alcohol, or sufficient alcohol so that when titrated with 0.1 N sodium hydroxide the solution will be a t least 50 per cent alcoholic a t the end of the titration. Heat this mixture on the steam bath, or reflux for 10 minutes, then titrate hot with 0.1 N sodium hydroxide, using phenolphthalein as indicator. 0.5 N alcoholic potassium hydroxide could be used, but it gives the same results when titrated cold, although they are not so accurate, since the potassium hydroxide is five times as 1
Received February 26, 1924. A. S. T. M. Tentative Methods, 1922, p. 389.
strong as the sodium hydroxide. Let B be the number of cubic centimeters of 0.1 N sodium hydroxide per gram of grease necessary to neutralize the fatty acids. Then B - A represents the number of cubic centimeters per gram of grease necessary to neutralize the fatty acids from the soap present. DETERMINATION OF SOAP The A. S. T. M. methods now proceed to separate the soap quantitatively, liberate the fatty acids, weigh them, determine their neutralization value, and add to the weight of the fatty acids, the weight of the sodium or calcium, corrected for the hydrogen of the fatty acids, corresponding to the neutralization value. Instead of such laborious procedure, the author separates a portion of the soap solution and determines its mean equivalent weight or neutralization value, or the equivalent in soap of 1cc. 0.1 N sodium hydroxide, and multiplies that by the value B - A . This gives the amount of soap per gram of grease and multiplied by 100 gives the percentage. PROCEDURE-After the titration of the naphtha or benzene solution of the fatty acids and oil to a permanent pink, add water to make 50 per cent alcoholic and allow to separate in a separatory funnel until two clear layers appear. Withdraw the lower layer and extract it once or twice with 25 cc. naphtha. Evaporate off the alcohol or nearly to dryness from the extracted soap solution and liberate the fatty acids hot in a solution of 100 cc. with (1:lO) sulfuric acid. Extract the fatty acids with ether in the usual manner and wash with distilled water until free of acid, the water washings being reextracted with ether to recover soluble fatty acids; add 80 cc. 95 per cent neutral alcohol, or sufficient to make the solution over 50 per cent alcoholic a t the end of the titration; titrate with 0.1 N sodium hydroxide. Before titration, it would be advisable to evaporate off most of the ether after the addition of the alcohol. The titration should be carried out hot, using phenolphthalein as indicator. Record titration as C cc. 0.1 N sodium hydroxide. Evaporate the entire solution to dryness in a fat flask on the steam bath or in vacuo, moisten with 95 per cent alcohol and dry again, place in an oven a t 105O C. for 10 minutes, cool in desiccator, and weigh as soda soap, X grams. Then 1 cc. of 0.1 N sodium hydroxide equals X/C grams of soda soap and the mean equivalent weight of the soda soap is X/C X 10,000. The mean equivalent weight of the corresponding calcium soap would be
+ (20-23) or (g X 10,000
For any soap subtract the equivalent weight of sodium (23) from the equivalent weight of the metal and add to the equivalent weight of the sodium soap. DETERMINATION OF METALS IN SOAP Dissolve a 10-gram sample in the alcohol-benzene mixture as for determination of free acid. Filter off the insoluble, washing with hot benzene, and evaporate filtrate and ash in a weighed platinum dish. Determine the metals in the usual quantitative way. Calculate the percentages of the metals in the original grease. Using the equivalent for the metal, calculate the percentage soap corresponding to it, according to its soap equivalent. Then calculate the ratio of the per-
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726
I N D U S T R I A L AhTD Ei\'GI,VEERING CHEMISTRY
Vol. 16, Xo. 7
centages of soap to.get the ratio of one soap to the other. Multiply these ratios by their respective soap equivalents and divide their sum by the sum of the ratios to get the mean equivalent weight. If there are three or more different metals, work first with>twoand then combine with the third and so on.
(4.545 X 303) 4- (2.660 X 306) = 304,4 4.545 2.660 Let the mean equivalent weight of the soap be M , then the percentage of anhydrous soap in the grease is ( B - A ) X (M)per 100 cent.
EXAMPLE-Metals present, Na and Ca; per cent Na in grease, 0.20 (difference); per cent Ca in grease, 0.30. Let the equivalent weight of the sodium soap be 306 and of the calcium soap 303.
Naphtha is used whenever the oil is to be recovered for further tests, although it has the disadvantage of creeping. Benzene is the better solvent to use for originally dissolving the soap, but it is difficult to remove the last traces in evaporation from the oil. It would be a good plan to run a t least one blank with all the reagents used throughout, to correct for impurities, etc.
+
Calorimetric Apparatus for t h e Measurement of Reaction Heats a t High Temperatures1" Particularly for the Heat of Carbonization of Coal By J. D.Davis PITTSEURGH EXPERIMENT STATION, BUREAU O F MINES, PITTSBURGH, PA.
EVELOPMENT of NATUREOF THE PROBLEM A n adiabatic twin calorimeter outfit was devised especially for calorimetric meththe determination of the reaction heat of coal during carbonization. For the carbonization of ods of precision durOne unit was made the exact duplicate of the other in so f a r as possible coal an elevated reaction ing the last fifteen years to the end that their capacities be the same and that their reaction temperature is required. has been of such importheat transfer constants be equal. Interchangeability of calorimeter The major decomposition ance that we may now unheating elements and calorimeter bombs was a feature that facilitated reactions begin a t around dertake the most difficult cross-checking, and a twin reciprocating stirrer insured equal heat 350" C., and continue until problems in thermal measinput to both units from stirring. the carbonization is comurement with good prospect The precision attained with the twin apparatus was of the order plete, when the coking of success. Owing largely of 0.013 per cent of the total amount supplied the calorimeter, and charge may have attained to the work of White3 of amounted to about 3.6 per cent of the differential quantity meas1000" C. or higher, dependthe Geophysical Laboratory ured. The total heat supplied was around 8500 calories, and the ing upon the carbonization a n d D i c k i n s o n 4 of the reaction heat of the coal sample tested was of the order of 30 calories. m e t h o d employed. I n Bureau of Standards, elecThis type of upparatus is recommended where small heats of reorder to determine the tric methods for temperaaction are to be determined at relatiuely high temperatures. The amount of heat involved in ture measurements of high limiting temperature is that at which the resistance of constantan the coking reactions, it is precision have been so imwire begins to oary quite widely, and is around 650" C. first necessary to supply sufproved as to render them ficient heat to raise the coal conveniently applicable to the measurement of temperature differences of the order of to the reaction temperature and to maintain it there against O.OO0lo C. These same investigators have also greatly im- radiation losses until the coking reactions are complete. Obproved methods for exact control of calorimetric environment, viously, it is necessary to measure accurately the heat thus particularly the controlled jacket method and the compen- supplied as well as that developed by the reactions. I n the method to be described herein, the former heat quantity was sating calorimeter method. Professor Richards5 and his students have devoted their from 100 to 300 times that of the latter-that is, the quantity attention to the improvement of adiabatic calorimetric sought. The main difficulties of the problem may be stated methods. Primarily as a result of this work, there are now as follows : available calorimetric methods of precision better than one 1-Determination of a relatively small portion of the total per mille which only require adjustment to the problem a t heat developed in the calorimeter. 2-The necessity for high temperatures within the calorimeter hand. Little work has been done, however, on the precise calling for the use of insulating materials which greatly increased measurement of reaction heats a t high temperature, and the thermal lag of the apparatus. this paper is concerned with the development of suitable 3-The time required for making a determination (that the apparatus for such work for the determination of the car- thermal reactions be complete) was so long as to exaggerate errors in estimation of thermal leakage. bonization heat of coal in particular. After trial of various types of single constant-volume 1 Presented before the Section of Gas and Fuel Chemistry a t the 66th calorimeters the twin calorimeter was adopted. The first Meeting of the American Chemical Society, Milwaukee, Wis., September 10 to 14, 1923. outfit was provided with a simple, covered water jacket, 2 Published by permission of the Director, U.S . Bureau of Mines. no precautions being taken to stir or control the water jacket 3 J . Am. Chem. Soc., 36, 2292 (1914). temperature. This proved entirely inadequate, and a com4 Bur. Standards, Bull. 11 (1915). plete water jarket with adiabatic control was provided. 6 Richards and Burgess, J. A m . Chem. Soc., 32, 446 (1910).
D
