Composite Samples of Milk. 149 



patron of the factory and is labeled with his name or 

 number. A small quantity of preservative (bi-chromate 

 of potash, bi-chlorid of mercury, etc., see 188) is added 

 to each jar these are placed on shelves or somewhere 

 within easy reach of the operator who inspects and 

 weighs the milk as it is received at the factory. When 

 all the milk delivered by a patron is poured into the 

 weighing can and weighed, a small portion thereof, 

 usually about an ounce, is put into the jar labeled with 

 the name or number of the patron. The samples are 

 conveniently taken by means of a small tin dipper hold- 

 ing about an ounce. This sampling is continued for a 

 week, ten days, or sometimes two weeks, a portion of 

 each patron's milk being added to his particular jar 

 every time he delivers milk. A test of these composite 

 samples takes the place of separate daily tests and gives 

 accurate information regarding the average quality of the 

 milk delivered by each patron during the period of 

 sampling. The weight of butter fat which each patron 

 brought to the factory in his milk during this time, is 

 obtained by multiplying the total weight of milk deliv- 

 ered during the sampling period by the test of the 

 composite sample, dividing the product by 100. 



177. This method of taking composite samples has been 

 proved to be practically correct. It is absolutely correct 

 only when the same weight of milk is delivered daily by 

 the patron. If this is not the case, the size of the various 

 small samples should bear a definite relation to the milk 

 delivered; one-sixteen hundredth, or one two-thousandth 

 of the amount of milk furnished should, for instance, be 

 taken for the composite sample from each lot of milk. 



