DETECTION OF ADULTERATIONS. 



I. ADULTERATION WITH WATER. 



By far the most common adulterant used for milk is 

 water. Tliis adulteration cannot always be detected by 

 ordinary market control tests since, as already stated, the 

 effect of the water which is added is often counteracted 

 by skimming the milk. The result is frequently in such 

 cases that the specific gravity is not essentially different 

 from that of the normal original sample. Sometimes it 

 is possible to discover such admixture by means of chem- 

 ical reactions. Such tests are based on the fact that in 

 almost every case the water used as a diluent contains 

 considerable quantities of salts such as calcium sulphate 

 and other sulphates and often traces of nitrates which are 

 foreign to pure milk. 



Pure milk contains only an exceedingly small amount 

 of sulphuric acid, never more than 0.3 per cent (calculated 

 to ash). In case a considerably larger amount is found, 

 the addition of water is indicated. The test is conducted 

 in the following manner : 50 c. c. of milk are treated with 

 acetic acid to precipitate the casein, filtered, and the fil- 

 trate evaporated, dried, and incinerated. The ash is taken 

 up with hot water and a few drops of hydrochloric acid ; 

 and the extract filtered, boiled, and treated with barium 

 chloride solution. After heating for some time the re- 

 sulting barium sulphate is filtered off and washed first 

 with hot dilute hydrochloric acid and then with boiling 

 water to remove the acid. The filter and contents are 

 dried, placed in a weighed crucible, ignited, and weighed. 



