October 15, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
(113' E'.) and that of the room 25" C. (77" I?.). The value of (hc f hr) A, using Equation 3, is found to be 24.1 Calories per hour per C. (53.2 B. t. u. per hour per O F.). Heat capacities of solutions and mixtures, in particular those used in the pulping industries, can be determined by the use of Equation 1.
CHEMICAL PREPARATIONS Undergraduate laboratory courses in industrial chemistry have inany uses for rotating autoclaves. The preparation of wood pulp is but one of the digestion processes which
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familiarize the student with important phases of the chemical industry. Other processes, especially those peculiar to geographical location, suggest themselves. The object of this paper has been to show that expensive research equipment can be also used for undergraduate instruction in industrial chemistry and chemical engineering, The intensive and general application of apparatus can justify the installation of equipment developed for special investigations. R E C E ~ VJune ~ D 15, 1932.
Estimation of Thallium after Oxidation with Bromine PHILIP E. BROWNING, Yale University, New Haven, Conn.
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T H E reagents employed for the oxidation of thallium, bromine has received little attention, although its action is rapid and complete. Sponholz (3) recommended it for the volumetric estimation of thallium, using the color of excess bromine to indicate when the reaction was complete. I n the description of this method he called attention to the necessity of frequent standardization of the bromine solution. The difficulties of such a volumetric procedure are quite obvious, If, however, the oxidized solution is treated with an alkali hydroxide in sIight excess, the immediate and complete precipitation of thallic hydroxide is effected. The delicacy of this reaction was first tested qualitatively, and it was found that in a volume of 10 cc., 0.1 mg. of thallium could be detected by the dark coloration of the thallic hydroxide, a delicacy which was rarely exceeded by such reagents as potassium iodide, chloroplatinic acid, or sodium cobaltinitrite. Sodium peroxide proved to be much less satisfactory as a means of detection. This test cannot be made in the presence of such elements as iron, manganese, cobalt, or nickel which give similar color changes due to oxidation. Quantitatively the results were as follows: A solution of thallous nitrate was made up and standardized by oxidizing four portions of 10 cc. each with potassium ferricyanide in the presence of potassium hydroxide (1, 2 ) , filtering off the thallic hydroxide on a weighed asbestos felt, and weighing the oxide after bringing it to constant weight a t a temperature
of 150" to 200" C. The mean of four closely agreeing results gave 0.1345 gram of thallic oxide Portions of 10 cc. each of this same solution were oxidized with bromine water in slight excess, the oxidized solutions precipitated, with or without gentle warming, with sodium or ammonium hydroxide, and the precipitates filtered off, heated, and weighed in the same manner as the precipitate from the ferricyanide treatment described above. Four closely agreeing results, ammonium hydroxide having been used as the precipitant, gave as a mean 0.1334 gram of thallic oxide; and another four, sodium hydroxide having been employed as the precipitant, gave a mean of 0.1344 gram of thallic oxide. The method was rapid, easy of manipulation, and certainly, when sodium hydroxide was used, of satisfactory accuracy. Obviously, those elements whose hydroxides are insoluble in excess of sodium or ammonium hydroxide must be absent when this method is applied. This necessitates the previous removal of thallium from most of the other elements, a procedure not unusual before the application of many gravimetric processes to the estimation of a single element.
LITERATURE CITED (1) Browning and Palmer, Am. J. Sci., 27, 379 (May, 1909). (2) Hillebrand and Lundell, "Applied Inorganic Analysis," p. 377, Wiley, 1929. (3) Sponholz, 2. anal. Chem., 31, 519 (1894); Chem. News, 67, 187 (1894). RECEIVEDMay 20, 1932.
An Improved Flask for Van Slyke Protein Analysis RAE PATTON, University of Minnesota, St. Paul, Minn. HE flask shown has been found to be an improved form for hydrolysis of proteins according to Cavett's modified Van Slyke nitrogen distribution method ( I ) . It consists of a 300-ml. Kjeldahl flask to which has been attached a side neck, in the manner of a Claissen flask. Several operations are performed in the flask, saving time and increasing accuracy. The protein sample is hydrolyzed, the hydrochloric acid is distilled off, the ammonia nitrogen is determined, and the total nitrogen in the humin fraction is determined, all in the same flask on the same sample. The advantages of this Kjeldahl-Claissen flask over the 250-ml. distilling flask recommended in the original method, are: (1) The double neck prevents foam from bubbling over into the standard acid during the ammonia determina-
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tion. (2) The additional s t r e n g t h of t h e K j e l d a h l flask makes it more suitable for t h e KjeIdahl digestion, etc.
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LITERATURE CITED (1) Cavett,
J. W., J.
Bid. Chem., 95, 335-43 (1932). RBCEIVED July 22,1932.
