176 H. S. H. WARDLAW. 



spirit on a filter surrounded by a steam coil which kept the 

 liquid hot. No protein could be detected in the filtrate 

 from this precipitation by means of Millon's reagent. This 

 reagent as used in the present case was capable of detect- 

 ing one part in 20,000 of protein in solution, a quantity 

 which would amount to about 0*25% of the protein esti- 

 mated. No sugar could be detected in the second washing 

 by means of Fehling's solution. This reagent, as used in 

 the present case was capable of detecting one part of 

 lactose in 8,000, a quantity which would amount to about 

 0*2% of the whole of the lactose present. No simple quali- 

 tative test for fat of a well-defined order of delicacy was 

 known, but a comparison of the results obtained by this 

 method with those obtained by another method (described 

 below) in which the fat was completely removed from the 

 milk before the estimation of protein showed that the 

 amount of any fat not removed by the washing was within 

 the experimental error. 



In samples 71 to 122 a modification of the above method 

 was used for the estimation of protein. Instead of a fresh 

 sample of milk being taken, an aliquot part of the aqueous 

 layer of the liquids obtained in the estimation of fat by the 

 Rose-Gottlieb method was used. The method thus modified 

 has the advantage that the fat and protein are both esti- 

 mated on the same sample of milk, and that the fat in the 

 liquid in which the protein is estimated has already been 

 completely removed. The quantity of milk required for 

 analysis is in this way much reduced, a determination of 

 both fat and protein being easily made on 5 cc. of milk. 

 Further, it is unnecessary to take precautions to keep the 

 liquids hot during filtration in order to keep fat in solution. 

 The first precipitation must, however, still be made from 

 boiling alcohol, or the precipitate will not come down com- 

 pletely, and hot alcohol is more convenient for the washings 

 than cold. Citric acid was added before the precipitation 



