14 EXPERIMENT STATION RECORD. [Vul. 36 



Kjeldahl modification for determination of nitrogen in nitro substitution 

 compounds, W. C. Cope {Jour. Indus, and Engin. Chem., 8 {1916), No. 7, pp. 

 592, 593). — The following procedui'e is described: 



About 0.5 gm. of the nitro substitution compound is accurately weighed and 

 placed in a 500-cc. long-necked Kjeldahl digestion flask. Thirty cc. of sulphuric 

 acid containing 2 gm. of salicylic acid is then added, and the niti'o compound 

 dissolved by rotating the flask or heating over a steam bath if necessary. After 

 cooling, 2 gm. of zinc dust in small proportions at a time is added, the flask 

 being continually rotated and cooled to prevent heating above room tempera- 

 ture. After all the zinc has been added the flask is rotated at 10 or 15 minute 

 intervals for about 1.5 to 2 hours, and then allowed to stand overnight at room 

 temperature. The flask is then gently heated over a small flame until the 

 evolution of fumes has ceased, brought to boiling, and the boiling continued 

 for from 1.5 to 2 hours, slightly cooled, 1 gm. of yellow 'mercuric oxid added, 

 and boiled for 1.5 hours longer. After cooling, 7.5 gm. potassium sulphate and 

 10 cc. more of sulphuric acid are added and the mixture again boiled for 1.5 to 2 

 hours. If the solution is clear and practically colorless the digestion is com- 

 plete. If not, 1 gm. more potassium sulphate should be added and boiling con- 

 tinued for some time. The distillation is then carried on and the determination 

 completed as is usual for all modifications of the method. 



In order to prevent low results, cooling during the addition of the zinc for 

 reduction and the long standing before heating the acid solution have been 

 found to be absolutely necessary. 



Apparatus for Kjeldahl determinations, W. W. Randall {Jour. Indus, and 

 Engin. Chcin., 8 {1916), No. 7, pp. 6S9. 640. fig. 1). — In the apparatus described 

 the acid fumes are carried off from the digestion flasks through properly fitted 

 calcium chlorid tubes which are connected with a larger tube through which the 

 fumes pass Into a large absorption flask. The apparatus is a modification of 

 that described by Sy (E. S. R., 28, p. 311). 



Sodium sulphate as a substitute for potassium sulphate in the Gunning' 

 modifications for determining nitrogen, W. L. Latsuaw {Jour. Indus, and 

 Engin. Chan., 8 {1916), No. 7, pp. 586, 587). — On account of the present high 

 price of potassium sulphate an endeavor was made to find a suitable substitute 

 The results of a series of determinations on materials ranging in nitrogen con- 

 tent from 0.039 to 14.95 per cent, using sodium sulphate in place of potassium 

 sulphate, are reported in tabular form, and clearly indicate that sodium sulphate 

 can be used in place of potassium sulphate for determining nitrogen in a variety 

 of substances. 



A modification of McCrudden's method for calcium, for the estimation of 

 calcium and strontium in the presence of phosphoric acid and a small amount 

 of iron, O. B. Winteb {Jour. Indus, and Engin. Chcm., 8 {1916), No. 7, pp. 60S, 

 60.'f). — The author, at the Michigan Experiment Station, has modified McCrud- 

 den's method (E. S. R., 23, p. 9) for the determination of calcium and stron- 

 tium, as follows: 



The solution containing the calcium or strontium or both is diluted to about 

 200 cc, a few drops of alizarin added, and then ammonium hydroxld until the 

 solution Is faintly alkaline. Dilute hydrochloric acid is then added to faint 

 acidity. To this solution 10 cc. of half-normal hydrochloric acid and 10 cc. of 

 2.5 per cent oxalic acid are added and the mixture boiled until the precipitate 

 becomes coarsely granulated. Saturated ammonium oxalate solution Is then 

 added, a few drops at a time, with constant stirring, until about twice the 

 amount necessary to precipitate all the calcium and strontium has been added. 

 The solution is cooled, 8 cc. of 20 per cent sodium acetate and about 15 cc. of 



