Chemical Analysis of Milk and Its Products. 227 



and ash, being subtracted from the total solids. It may 

 be determined directly by means of a polariscope, or 

 gravimetrically by Fehling's solution; only the former 

 method, as worked out by \Yiley, 1 will be given here. 



The specific gravity of the milk is accurately deter- 

 mined, and the following quantities of milk are meas- 

 ured out by means of a 100 cc. pipette graduated to .2 

 cc. (or a 64 cc. pipette made especially for this purpose, 

 with marks on the stem between 63.7 and 64.3 cc.), ac- 

 cording to the specific gravities given: 1.026, 64.3 cc. ; 

 1.028, 64.15 cc.; 1.030, 64.0 cc.; 1.032, 63.9 cc. ; 1.034, 

 63.8 cc. ; 1.036, 63.7 cc. These quantities refer to the 

 Schmidt-Haensch half-shadow polariscopes, standard- 

 ized for a normal weight of 26.048 grams of sugar. The 

 milk is measured into a small flask graduated at 100 cc. 

 and 102.6 cc. ; 30 cc. of mercuric-iodid solution (pre- 

 pared from 33.2 grams potassium iodid, 13.5 grams mer- 

 curic chlorid, 20 cc. glacial acetic acid and 640 cc. 

 water) are added; the flask is filled to 102.6 cc. mark 

 with distilled water, the contents mixed, filtered through 

 a dry filter, and when the filtrate is perfectly clear, the 

 solution is polarized in a 200 millimeter tube. The 

 reading of the scale divided by 2, shows the per cent, 

 of lactose (milk sugar) in the milk. Take five readings 

 of two different portions of the filtrate, and average 

 the results. 



260. f. Ash. About 20 cc. of milk are measured into 

 a flat-bottom porcelain dish and weighed ; about one-half 

 of a cc. of 30 per cent.-acetic acid is added, and the 

 milk first dried on water bath and then ignited in a 



1 Agricultural Analysis, III, p. 275 ; Am. Chem. Jour., 6, p. 289 et scq. 



