1919] AGRICULTURAL CHEMISTRY — AGROTECHNY. 11 



changes were thus traced. Determinations were made by the colorimetric and 

 electrometric methods in the water and alcoholic extracts of the silage. 



The acidity of the alcoholic extracts of the three kinds of silage was greater 

 than that of the water extract when the titration was made to the point of color 

 change for phenolphthalein. With the electrometric method there was no sig- 

 nificant difference between the results obtained on the water extract and on 

 the alcoholic extract. The differences in the colorimetric method are considered 

 to be due to colored matter extracted by the alcohol which masks the end point. 

 Most of the acidity was found to develop in the first 15 days. The maximum 

 acidity was reached in from 40 to GO days. The acidity of the alfalfa was greater 

 than that of the sweet clover silage. The addition of corn meal to sweet clover 

 increased the acidity of the silage. 



The amount of amino nitrogen was found to be practically the same in the 

 water and in the alcoholic extracts. The amount of amino nitrogen in silage 

 made from alfalfa alone was larger than in that made from sweet clover alone. 

 The addition of corn meal to sweet clover did not influence the amount of amino 

 nitrogen developed. The amount of nitrogen in amid form as determined by 

 Stutzer's method was slightly larger than the amount of nitrogen in amino form 

 as determined by the formaldehyde method. The nitrogen in amid form was 

 approximately one-half of the total nitrogen. Approximately two-thirds of the 

 total nitrogen in silage was soluble in water and in 50 per cent alcohol, the 

 solvent action of the two being nearly the same. 



From the data reported the authors conclude that silage can be made from 

 sweet clover alone with less difficulty than from alfalfa alone. 



Cholesterol in milk, W. Denis and A. S. Minot (Jour. Biol. Chem., 86 (1918), 

 No. 1, pp. 59-61; abs. in Chem. Abs., 12 (1918), No. 23, p. 2616).— Determina- 

 tions of cholesterol in cow's milk and in human milk by Bloor's colorimetric 

 method are reported, together with corresponding fat determinations, using the 

 Babcock method for cow's milk and Bloor's nephelometric method (E. S. R., 32. 

 p. 312) for human milk. 



The results show a direct and proportional variation of the cholesterol with 

 the total fat content of cow's milk. This proportionality is also noted in human 

 milk, but with many exceptions. 



The authors suggest that the regular results obtained with cow's milk, in 

 distinction to the variations occurring in human milk, are perhaps due to 

 the fact that the samples of cow's milk were obtained from a single dairy and 

 from animals fed on exactly the same ration, while the human milk was taken 

 from women living under a great variety of conditions and with a corresponding 

 lack of uniformity in food intake. It is pointed out that the higher level of 

 cholesterol in the human milk may be attributed to the higher cholesterol con- 

 tent of the food of nursing mothers as compared with that of cows. 



Influence of the preparation on the specific weight and refraction of milk 

 serum, N. Schoorl (Pharm. Weckbl., 55 (1918), No. 36, pp. 1222-1880; Chem. 

 Weekbl, 15 (1918), No. 36, pp. 1089-1097).— This is a criticism of the conclusions 

 of Van der Harst and Koers previously noted (E. S. R., 39, p. 805), with a reply 

 to the criticism by these authors. 



The acidity of milk and whey, W. van Dam (Versing. Landbouwk. Onder- 

 zoek. Rijkslandbouwproefstat. [Netherlands], No. 22 (1918), pp. 1-24, fiff- D- — 

 The apparent difference in the acidity of the milk serum from spontaneously 

 soured milk and of sour whey is explained by the buffer action of the constituents 

 of the milk and whey. A table is given of the hydrogen-ion concentration of 

 whey, peptonized whey, and peptonized milk at different dilutions. 



The influence of the acidity of milk on the velocity of the inactivation of 

 peroxidase by heat, A. Bouma and W. van Dam (Verslag. Landbouwk. Onder- 



