DETECTIOX OF STERILISED MILK. 195 



Condensed unsweetened milk, which, has been diluted to the 

 original volume with water, has all the analytical characteristics 

 of sterilised milk. It throws up its cream rather less readily 

 even than sterilised milk. No. 6 in Tables XL\. and XLVI. was 

 diluted condensed milk. This is in no way due to the fact that 

 it has been condensed, but is owing to the sterilising process that 

 it has undergone. There appears to be no good method of dis- 

 criminating between condensed milk diluted with water and 

 sterilised milk. If a water containing large amounts of nitrates 

 has been used for diluting the condensed milk, a strong diphenyl- 

 amine reaction will indicate the probability that water has been 

 added ; this test is not of a sufficiently absolute character to be 

 relied on. This is to be regretted. The subject has been con- 

 sidered of sufficient importance by the British Dairy Farmers' 

 Association to induce them to offer a gold medal for the discovery 

 of such a method. 



Detection of Sterilised Milk in New Milk. — To distinguish 

 new milk on the one hand from milk which has been sterilised 

 on the other, the following methods may be employed : — 



(1) Place 100 c.c. of milk in a graduated cylinder (or fill a 

 " creamometer ") and allow it to stand for six hours at a tem- 

 perature of 60° F. (15'5° C.) ; note the percentage of cream. If 

 less than "2 a per cent, of cream for each 1 per cent, of fat in the 

 milk has risen to the surface, the milk may be considered suspi- 

 cious. If the quantity of cream falls markedly below 2 per cent. 

 for each 1 per cent, of fat, it is highly probable that sterihsed 

 milk is present. 



(2) Estimate the albumin by the method of Hoppe-Seyler 

 or, better, that of Sebelein. If less than 0'35 per cent, is found, 

 sterilised milk may be considered to be present. 



(3) Estimate the milk-sugar by the polariscope, and also 

 gravimetrically in duphcate ; if the difierence between the two 

 estimations be more than 0"2 per cent., it will be corroborative 

 evidence of the presence of sterilised milk. 



(I) To about 5 c.c. of milk add as much powdered para- 

 phenylene-dianiine as will lie on the point of a knife, and shake 

 well ; on the addition of a drop or two of a 10-volume solution 

 of hydrogen peroxide fresh milk gives a blue coloration ; " pas- 

 teurised " milk gives a similar reaction, not, however, so marked ; 

 while " sterilised ' milk gives no coloration within ten minutes. 

 A mixture of " sterilised " and fresh milk will give the characters 

 of '■ pasteurised " milk. 



The hydrochloride of meta-phenylene-diamine may be sub- 

 stituted with advantage for the para-compound. The coloration 

 is paler, and not quite so quickly developed. By shaking with 

 an equal volume of amyl alcohol the blue substance is dissolved in 



