30 DAIRY ANALYSIS 



tube, and add 30 c.c. of ether, cork the tube, and 

 shake well ; allow the tube to stand till the ether has 

 separated in a clear layer; remove as much ether as 

 possible, preferably by means of washbottle tubes, to 

 a weighed flask ; add about 20 c.c. more ether, 

 shake well, allow the ether to settle clear, and 

 remove as before, and again add about 20 c.c. 

 of ether, shake, allow to settle, and remove 

 the clear layer. Distil off the ether, dry, and 

 weigh as above. 



Gottlieb's Method. Place 5 c.c. of milk in a 

 stoppered tube, add successively 0.5 c.c. of 

 ammonia, 5 c.c. of alcohol, 12^ c.c. of ether, 

 and 12 \ c.c. of petroleum ether ; mix after 

 each addition, and allow to stand ; when a 

 clear layer has separated, mix again, allow to 

 separate, mix once more, and allow the clear 

 Stokes I a 7 er ^ completely separate. 

 Tube Remove the ethereal layer as completely 



as possible by washbottle tubes to a flask, 

 and add and remove three successive portions of a 

 mixture of equal parts of ether and petroleum ether. 

 Evaporate the solvent, dry, and weigh as above. 

 Extract with petroleum ether and weigh the empty 

 flask. 



Estimation of Milk Sugar. This may be estimated 

 either polarimetrically, or gravimetrically ; the results 

 in either case are expressed as anhydrous sugar. 



Polarimetric Estimation. 50 c.c. of milk are measured 

 into a dry flask, and a quantity of water equal in cubic 

 centimetres to the sum of 



(a) The degrees of gravity divided by 20. 

 (6) The percentage of fat divided by 1.8. 

 (c) A. quantity to convert scale readings into 

 percentages of anhydrous sugar ; if the scale is 

 in angular degrees and a 200 mm. tube is used, 

 this is|543 c.c. (or 5 c.c. with a 198.4 mm. tube). 

 1.5 c.c. of Wiley's acid mercuric nitrate solution (see 

 Appendix) is added, and the whole well mixed by 



