MILK. 225 



to dryness and igniting the residue. It is advisable only to 

 prepare small quantities at a time, using about 20 g. of 

 copper sulphate. 



7. Determination of Milk-sugar. Dilute the filtrate and 

 wash-water freed from the albumin (see the " Determination 

 of Total Proteid according to Bitthausen and Mu.nk ' ' or the 

 method of Soxhlet given below) to a definite volume (with 

 20 cc. of milk to 140 or 160 cc.), fill a burette with this solution, 

 and titrate 20 cc. of Fehling's solution + 80 cc. of water with 

 it. (See chapter on " Urine. ") Twenty cubic centimeters 

 of Fehling's solution correspond to 0.135 g. of anhydrous 

 milk-sugar (C 12 H 22 U ). 



Instead of titrating we may add to 40 cc. of Fehling's 

 solution + 80 cc. of water, heated to boiling, 30 cc. of the 

 above fluid, continue the heating for six to seven minutes, 

 collect the precipitated cuprous oxide on a weighed filter 

 and weigh as such, or convert it into copper sulphide or 

 metallic copper and weigh this. We may also remove the 

 casein and albumin in one operation according to Soxhlet. 

 Twenty-five cubic centimeters of milk are mixed with 400 cc. 

 of water, a few drops of acetic acid are added, and the solu- 

 tion heated to boiling. When cold dilute to 500 cc. and fil- 

 ter through a dry filter. One hundred cubic centimeters 

 of the filtrate = 5 cc. of milk are then boiled with 50 cc. of 

 Fehling's solution for six minutes, etc. Since the reduction 

 equivalent of milk-sugar for copper oxide in alkaline solu- 

 tion is not constant, according to Soxhlet, but varies ac- 

 cording to the concentration of the milk-sugar solution, an 

 empirical table (see pages 226 and 227) must be used for 

 the calculation. This has been established by Soxhlet and 

 calculated directly for milk-sugar by E. Wein. 



8. Determination of the Total Phosphorus. Ten cubic 

 centimeters of milk are dropped upon 30 g. of the oxidizing 

 mixture, contained in a platinum dish, evaporated to dry- 



