CHEMISTRY. 17 



ammonium molybdate in 1 liter of water. Tlie phosphoric acid is deter- 

 mined by comparing the coloration thus produced with tbat of stand- 

 ard solutions of phosphate to which an equal 'quantity of molybdic 

 solution has been added. 



Note on the estimation of citrate-soluble phosphoric acid in 

 Thomas slag, M. Passon {Ztsehr. Angeic. Chem., 1897, No. 23, pp. 746- 

 749). — Instead of the solution used by Wagner, the author recommends 

 a solution containing 140 gm. crystallized citric acid and 30 gin. tri- 

 potassium citrate in 1 liter. This solution gives results identical with 

 the Wagner solution and is much easier to make. The tripotassium 

 citrate is prepared by adding to a solution of citric acid rather more 

 than enough potassium hydrate to neutralize the acid, evaporating the 

 solution on a water bath until it begins to crystallize, allowing it to 

 cool, and then stirring until a complete crystallization has taken place. 

 The mother liquor is then drawn off, the salt washed with as little 

 water as possible until the alkaline reaction disappears, then several 

 times with alcohol and ether, and finally dried between folds of filter 

 paper. — J. b. lindsey. 



A new method for the estimation of starch in grains, L. Lindet 

 (Ztsehr. Angeiv. Chem., 1898, No. 7, p. 166). — Ten grams of the ground 

 grain is treated for 24 hours at 40 to 50° C. with a solution containing 

 2 per cent of pepsin and 1.5 per cent of hydrochloric acid. The solu- 

 tion is then brought into a small sack made of fine bolting cloth (SO to 

 100 mesh) and suspended in water until the starch appears to be 

 entirely removed. The water should be changed frequently during 

 the washing. The combined waters are filtered through a tared filter 

 to collect the starch. The paper should be dried, first at 50° C. and 

 later at 105° C. to constant weight. — J. b. lindsey. 



On the practical application of the refractometer in butter 

 examination, A. J. Swaying (Laudic. Vers. Stat, 49 (1897), No. 1-5, 

 pp. 341-347). — The author states that shipments of pure butter from 

 Holland and Friesland to England have repeatedly been held to be 

 suspicious on account of being below the limit for volatile fatty acids 

 adopted by English chemists. This difficulty, it is believed, could be 

 avoided by the use of the refractometer, which is also a great saving 

 of time. 



The results are tabulated for 024 samples of butter examined with 

 the refractometer and for volatile fatty acids. Of these, 353, or 56 per 

 cent, showed a refractive index of 52.5° or less; and 127, or 20 per cent, 

 showed a refractive index of 52.5 to 54°. These 480 samples were 

 proved to be pure, natural butter. The remaining 144 samples, or 24 

 per cent, showed a higher refractive index (than 54°) and were in part 

 identified as adulterated. 



In the case of butter containing admixtures of other fats it is con- 

 sidered necessary to make an examination with the polarizing micro- 

 scope, in addition to determinations of the volatile fatty acids and the 



