310 PHYSIOLOGICAL CHEMISTRY. 



ture of acetic acid and concentrated sulphuric acid, warmed 7-8 

 minutes on the water-bath, the mixture placed in graduated tubes, 

 and these in the centrifugal machine at -j- 50 C. The height of 

 the layer of fat gives its quantity. 



In determining the milk-sugar first the albumin is removed. 

 For this purpose we precipitate either with alcohol, which must be 

 evaporated from the filtrate, or by diluting with water, and re- 

 moving the casein by the addition of little acid, and the lactalbumin 

 by coagulation at a boiling heat. The sugar is determined by 

 titration with FEHLING'S or KNAPP'S solution (see Chap. XIV). 

 The principle of titration is the same as for the titration of 

 sugar in urine: 10 c.c. of FEHLI^G'S solution corresponds to 

 0.067 grm. milk-sugar; 10 c.c. of KNAPP'S solution corresponds to 

 0.0311-0.0310 grm. milk-sugar, when the saccharine liquid con- 

 tains about ^-1$ sugar. In regard to the modus operandi of the 

 titration we must refer the reader to more complete works and to 

 Chapter XIV. 



Instead of the volumetric determinations the following steps 

 may be taken: A measured quantity of the milk-sugar solution is 

 treated with an excess of FEELING'S solution, boiled, the copper 

 suboxide filtered and reduced in a current of hydrogen, and the 

 metallic copper weighed. SOXHLET has given a table (Journal fiir 

 praktische Chemie, 1880) which simplifies the calculations in such 

 cases. 



The sugar may also be determined by the polariscope, and with 

 ease, because the filtrates containing milk-sugar are generally color- 

 less. The determination is quickly performed but does not give 

 exact results. 



The quantitative composition of cow's milk is variable, The 

 average obtained by KONIG is as follows in 1000 parts : 



Water. Solids. Casein. Albumin. Pats. Sugar. Salt. 

 874.2 125.8 28.8 5.3 36.5 48.1 7.1 



34.1 



The quantity of mineral bodies in 1000 parts of cow's milk is, 

 according to the analyses of SOLDNEE, as follows : K 2 1.72, 

 Na 2 0.51, CaO 1.98, MgO 0.20, P 2 5 1.82 (after correction for 

 the nucleins), Cl 0.98 grms. BUNGE found 0.0035 grm. Fe 2 3 . Ac- 

 cording to SOLDNER, the K, Na and Cl are found in the same quan- 

 tities in whole milk as in milk-serum. Of the total phosphoric 

 acid 36-56$ is not dissolved and also 53-72$ of the lime. A part of 

 this lime is combined with the casein; the remainder is found 



