242 THE CHEMICAL CONTROL OF THE DAIRY. 



Eleven e.c. of the alkaline salt solution, 10 c.c. of milk, and 

 0'6 CO. of isobutyl alcohol are placed in a butyrometer, which is 

 closed with a stopper, and the contents mixed, and immersed in 

 water at 45° for three minutes, and after shaking the tube is centri- 

 fuged, and the fat read off after again placing in water at 45°. 

 These results are the same as those given by the acido-butyro- 

 metric method, but the accuracy is somewhat less. The amount 

 of isobutyl alcohol added must not be varied. 



Sichler's sinacid method is very similar ; 10 c.c. of salt solution, 

 containing 15 per cent, of trisodium phosphate and 1 per cent. 

 of trisodium citrate, 10 c.c. of milk, and 1 c.c. of isobutyl alcohol 

 are placed in a butyrometer, and well mixed. The mixture is 

 heated to 75° to 90°, again well mixed, and centrifuged for one 

 minute. The tube is placed in water at 70°, and the fatty layer 

 read off. The isobutyl alcohol is usually coloured, and the 

 colour passes into the fatty layer, facilitating reading. 



The Control of Milk during Delivery to Customers. 



A very important part of the work of the dairy chemist is the 

 control of the men employed in delivering milk. It is evident 

 that a man on a milk round, being under no supervision for a 

 greater part of the time, has ample opportunities, should he be 

 so disposed, to adulterate or " lengthen " the milk of which he 

 has temporary charge. He may also, with the best intentions 

 possible, unwittingly deteriorate the quality of the milk by 

 allowing the cream to rise on the milk, and serving some cus- 

 tomers with the richer portion, thereby leave a poorer quality 

 for others. For the purpose of this control it is necessary to 

 take three series of samples. 



(1) Samples representative of the raixed bulk of milk that is placed in 

 charge of the man. 



(2) Samples taken in the streets in the course of dehvery. 



(3) Samples of the small quantities of milk returned. 



The first and third samples should be taken by a foreman or 

 other responsible person, preferably in the presence of the man ; 

 the foreman should be responsible for their conveyance to the 

 laboratory. 



The second series should be taken by an intelligent and respons- 

 ible person, who should receive instructions to take samples at 

 irregular intervals, and to avoid any semblance of rotation, 

 in order that the man shall not be ajjle to form an idea when 

 he may expect a visit. He may be, with advantage, mounted 

 on a bicycle if the area of delivery is large. 



The first and third series may be conveniently taken in sample 

 cans, while the second series may be taken in five-ounce bottles, 



