CHAPTEE VII. 



ASS. 



IF the milk-solids be ignited, the organic matter is de- 

 stroyed, and the inorganic matter or ash remains behind. 

 The operation is managed in a very simple manner. The 

 small platinum dish containing the milk-solids from 5 c. c. 

 of milk is placed on a small triangle, either of platinum, or 

 of iron- wire, or of iron-wire covered with tobacco-pipe. The 

 last mentioned is an admirable form of support, and is very 

 well known to chemists. The flame, either of a spirit-lamp, 

 or of a Bunsen burner, is then made to play upon the plati- 

 num dish. By and by the organic matter is burnt up, and 

 a grey ash remains behind. The platinum dish and its con- 

 tents are then allowed to cool, and weighed. After subtract- 

 ing the weight of the dish, the weight of the ash remains. 

 This, multiplied by 20, equals the number of grammes of 

 ash or mineral matter contained by 100 c. c. of milk. 



The importance of a determination of ash depends upon 

 the fact that the correctness of it at once answers the ques- 

 tion whether or not the milk has been adulterated with 

 chalk, salt, or other inorganic impurity. I have made hun- 

 dreds of determinations of ash, and not yet come across a 

 single case of adulteration of this kind. 



As will be seen on looking back, the quantity of ash con- 

 tained by 100 c. c of milk is between 0.7 and 0.8 grammes. 

 Now, suppose the milk to be watered with, say London 

 water. In such a case the ash would be diminished, inas- 



