ii BUTTER 141 



be entirely freed from fat, otherwise when it dries it is difficult 

 to remove from the glass. The dish containing the solids not 

 fat is now dried for a couple of hours at 100 C., after which the 

 residue is brought on to the filter which was previously used, 

 and by washing repeatedly with petroleum ether it is freed 

 completely from fat. When all fat has been removed a drop of 

 the filtrate leaves no residue when evaporated on a watch-glass. 

 The filter containing the solids not fat can then be dried and 

 weighed in the usual way. 



IV. DETERMINATION OF PROTEIN. 



This cannot be done successfully by the Kjeldahl method 

 unless most of the fat has been removed, for otherwise an 

 objectionable amount of frothing takes place. The best way is 

 to treat the butter as in the determination of the solids not fat, 

 only a larger quantity of butter should be taken, and the filter 

 need not be washed entirely free from fat. 



The filter and the solids not fat are then treated in the usual 

 way, and the amount of nitrogen which is obtained is multiplied 

 by 6'37. The percentage of nitrogen in the filter paper can be 

 determined by analysing a few of the same kind and then 

 deducting that which is due to the filter from the above 

 result. 



V. ESTIMATION OF COMMON SALT. 



To estimate the total amount of ash, the butter is treated as 

 for the solids not fat, the filter and the residue then carefully 

 ignited in a platinum dish, and the weight of the filter ash 

 deducted. The weight which is thus obtained is the total ash. 

 The ash is then treated with water, filtered, and the sodium 

 chloride determined by titration with N/10 AgN0 3 , potassium 

 chromate being used as an indicator. 



By subtracting the amount of sodium chloride so obtained 

 from the total ash, there is left the quantity of milk salts (crude 

 ash) present in the butter. 



VI. PROOF OF PASTEURISATION. 



To find out whether the cream used in making a butter has 

 been pasteurised at a temperature of 80 G. or more Storch's 



