OF ARTS AND SCIENCES. 



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all the fat ; the benzine is decanted, a fresh portion poured on and 

 allowed to stand half an hour ; this is poured off, the dish rinsed with a 

 little fresh benzine, allowed to stand a few minutes until it has all 

 evaporated, again dried in the air bath at 105°, and weighed ; the loss 

 gives the fat. The residue remaining on the dish is of course the 

 solids not fat. 



Ash. The dish is then ignited over a Bunsen burner, and again 

 weighed, the residue in this case being the ash. With a dish of the 

 size spoken of, all the carbon burns off quickly and readily, and leaves 

 the ash perfectly white. 



The above determinations are all that are essential to determine the 

 purity of a sample of milk, and, as will be seen, consume but little 

 over 100 cc. of milk : 150 cc. are ample for the full analysis as followed. 

 In order to determine the cheese and sugar, 25 cc. of milk were taken 

 and diluted with about 50 cc. of water, the mixture was gently warmed, 

 and a drop or two of acetic acid added with gentle stirring ; it was 

 allowed to cool and then filtered on a weighed filter, and washed with 

 about 200 cc. of cold water. The filtrate was made up to 5U0 cc, and 

 this solution was titrated with a normal solution of cupric sulphate 

 made by dissolving 34.65 grammes of crystallized cupric sulphate in 

 200 cc. of water, adding to this solution a solution made by dissolving 

 173 grammes of sodio-potassic tartrate in 480 cc. of caustic soda solution 

 of 1.14 specific gravity. The whole is then made up to a litre; 10 cc. 

 of this solution were then placed in a fiask diluted with 40 cc. of water, 

 and brought to the boiling point ; the diluted whey was then allowed 

 to flow into the solution until it no longer gave a brown color, when 

 filtered, acidified with acetic acid and tested with potassic ferrocyanide. 

 The following, table gives the per cent of milk sugar, when 25 cc. of 

 the milk are taken, and the whey diluted to 500 cc. 10 cc. of the cop- 

 per solution, which equals .067 grammes of milk sugar, are employed. 



PER CENT OF SUGAR. 



