514 EXPERIMENT STATION RECORD. 



After thoroughly mixing the contents of the flask, add a small thimble- 

 ful of pulverized or reduced iron to prevent bumping, connect the flask 

 with the condenser, and distil the ammonia into standard acid, heating 

 cautiously at first to prevent frothing. 



Method of determining nitrites in waters, L. Eobin (Jour. Pharm. 

 et Ghim.j G. ser., 7 (1898), No. 12, pp. 575-577; abs. in Bui. Assoc. Ghim. 

 Sucr. et Distill., 16 (1898), No. 1, pp. 83, 84). — This method is based upon 

 the principle that when potassium iodid and acetic acid are added to a 

 solution containing nitrites an amount of iodin is set free which is pro- 

 portional to the amount of nitrites present. 



To 50 cc. of the water to be examined add 2 cc. of a 20 per cent solu- 

 tion of pure potassium iodid and 2 cc. glacial acetic acid, stir and allow 

 to stand exactly one-half hour, add a small amount of starch, and titrate 

 with a solution of sodium hyposulphite prepared by diluting 50 cc. of 

 decinormal solution to 1 liter. 



A table is given which shows the amount in milligrams per liter of 

 nitrous acid corresponding to the number of cubic centimeters of sodium 

 hyposulphite used when 50 cc. of the water is taken for the test. 



Concerning casein and its cleavage products in peptic digestion, F. Alex- 

 ander (Ztschr. Physiol. Chem., 25 (1898), No. 5-6, pp. 411-429).— A study of the 

 properties of casein prepared by the Hamraarsten method, and of the products 

 resulting in the fractional digestion with pepsin-hydrochloric acid. 



The estimation of potash in soils, C. L. Penny (Delaware Sta. Bpt. 1897, pp. 

 146-163, figs. «?).— See also Bulletin 36 of the station (E. S. R., 10, p. 134). 



A new volumetric method for the determination of copper, R. K. Meade 

 (Jour. Amer. Chem. Soc., 20 (1898), No. 8, pp. 610-613).— -The copper is precipitated as 

 cuprous thiocyanate, changed to oxid by heating with caustic alkali, treated with 

 an excess of ferric chlorid or sulphate with a little dilute sulphuric acid, filtered, and 

 the filtrate titrated with permanganate. The copper reduces a corresponding amount 

 of the iron from the ferric to the ferrous form, and the iron equivalent to the per- 

 manganate multiplied by 1.125 gives the amount of copper in the sample. 



The methods for examination of milk and its products, H. Tiemann (Die 

 Untersuchungsmethoden der Milch und deren Producte. Leipsic: M. Heinsius Xachf., 

 1898, pp. 61).— This is intended for food chemists, and deals especially with the 

 methods employed in the control of butter and milk. 



The determination of water in butter, margarin, etc., by means of acid- 

 butyrometry, N. Gerber and M. M. Craandijk (Milch Zttj., 27 (1898), No. 38, pp. 

 593-595). — The results of 15 trials of the method, which is described, in comparison 

 with the gravimetric results, are considered sufficiently exact for creamery and 

 police control purposes. 



The relations between the specific gravity and the insoluble fatty acids of 

 butter and other fats, N. Leonard (Analyst, 23 (1898), Nov., pp. 282, 2S3).— Four 

 years ago the author found, on examination of 33 samples of butter, that the results 

 might be represented by the formula y = k (1 — x), in which y is the percentage of 

 insoluble fatty acids, x the specific gravity at 100° F., and k a constant the mean 

 value of which was found to be 951^1.6. Recently 30 additional samples were 

 examined, and k was found to have the mean value 951 ^ 1.8. "This close agree- 

 ment with the previous result is interesting as showing the constancy of the general 

 character of the adulterants employed." The results obtained by calculation on 

 the above basis and by determination of the insoluble fatty acids are given. 



