372 THE CHEMICAL CONTROL OP THE DAIRY. 



as possible with his other duties ; this may introduce variations 

 in the plan of work described, by curtailing it, but the general 

 procedure will remain the same. 



The main duties of the dairy chemist are to see that the milk 

 received from the farms and supplied to the public is pure and 

 contains its due proportion of cream ; that the cream and butter 

 are of good quality and of uniform composition ; that the skimmed 

 or separated milk is as poor as possible in fat ; and that the 

 water used is free from pollution ; as. also to elucidate the com- 

 plaints of the customers by examining the product complained 

 of. 



Samples and Sampling, The main difficulty in keeping a 

 uniform quality of milk is due to the rising of cream whenever 

 milk is allowed to be at rest. The attention of the chemist 

 should be devoted to studying the conditions under which the 

 milk is distributed in the dairy to which he is attached, and to 

 discover how to prevent this separation of cream during distri- 

 bution. For the proper performance of his duties he must be 

 provided with samples of milk at all possible stages, from the 

 entrance of the milk into the dairy till the final return of the 

 small quantities of milk left after distribution ; these samples 

 should, if possible, be examined at once and before the milk has 

 passed to the next stage of delivery. This is only practicable in 

 large dairies where the chemist has no other functions. It is 

 advisable that persons employed in sampling the milk should 

 be under the control of the chemist so far as this duty is con- 

 cerned, as upon the proper sampling of the milk the whole value 

 of his work depends. In certain cases where more value than 

 usual is attached to the examination, the chemist should person- 

 ally supervise, or even perform, the sampling. 



The samples may be divided into two kinds, bulk-samples and 

 samples taken during delivery. In the former case, the object to 

 be attained is to take a sample in which the various constituents 

 shall bear the same relative proportion in the sample as in the 

 bulk. In the latter, the bulk from which the sample is taken 

 will be of known composition, and the object of taking the sample 

 is to test the person from whom it is taken ; no attempt must 

 then be made to take an average bulk sample, but the person 

 giving the sample should furnish it in the same manner as he 

 would furnish milk for sale. The taking of the latter class of 

 samples presents no difficulty ; the only precaution to be observed 

 is that the bottle into which the sample is poured is clean and 

 dry, and that it has a well-fitting cork. The proper sampling 

 of a large bulk of milk is by no means easy ; the bulk to be 

 sampled will be, in most cases, a churn, and the milk in these 

 should be mixed with a stirrer consisting of an iron rod carrying 



