48 DAIRY ANALYSIS 



treated similarly, is added ; the fat is estimated by the 

 Gerber method (or one of the gravimetric methods), 

 and the result is increased by one-twentieth ; this 

 method is available if the milk is not too old, and 

 serves excellently for control work. 



An estimation of total solids may be made after 

 neutralising the acid with strontia solution ; an 

 estimation of the acidity is made as usual (p. 15), a 

 weighed quantity being used instead of a measured 

 amount, and a proportionate amount of strontia solu- 

 tion added to the weighed quantity of milk taken for 

 total solid estimation ; from the weight of total solids 

 0.00428 gramme should be deducted for each cubic 



centimetre of strontia added. 

 10 



The ash is estimated as usual, but 0.00738 gramme 

 should be deducted from the weight of the ash for each 



cubic centimetre of strontia solution added. 

 10 



The fat estimation is preferably made by the Store h 

 method (an addition of strontia solution being made as 

 in the total solid estimation) or the Gottlieb method ; the 

 Werner-Schmid method is also available, though it tends 

 to give high results with very sour samples owing to the 

 solubility of lactic acid in ether. 



Other determinations are made as for milk, except 

 that the quantities taken are all weighed and not 

 measured. The total nitrogen is a useful datum. 



The aldehyde method does not give exact results for 

 proteins. 



The methods used in the Government laboratory 

 include the determination of alcohol, volatile acids, and 

 ammonia, and from these, the solids lost by the various 

 fermentations undergone by the milk are reconstructed. 

 The following description is condensed from Dr. 

 Thorpe's report : 



Alcohol. To 75 grammes of sour milk half the 

 caustic soda solution necessary to neutralise is added, 

 and the mixture is distilled : to the distillate is added 



