'238 THE CHEMICAL CONTROL OF THE DAIRY. 



This table should be checked by a gravimetric method, and 

 may require a slight correction added or subtracted, which may 

 vary with each pipette. 



The cream should be as near 15'5° C. (60° F.) as possible, but 

 the error due to temperature is very small and is less than the 

 errors of reading, etc. 



The pipette does not deliver the same weight of a cream with 

 20 per cent, of fat as of one with 30 per cent, of fat ; this has 

 been allowed for in the table. 



Sour Milk. — Well mix the sample by whisking for a few 

 minutes with a brush made of fine wires ; pour about 15 grammes 

 into a small beaker and weigh ; transfer from 10 to 11 grammes 

 to the bottle and weigh again to get the weight added ; add 

 water to make up 11 "22 grammes. Proceed as before. 



11 '22 



Calculate : Fat in sour milk = reading x 



wt. taken 



An alternative method is to add to each 100 grammes 5 c.c. 

 ■of strong ammonia and treat as a milk ; increase the result by 

 one-twentieth. 



Clotted Cream, Butter, Cheese, etc. — Well mix the sample (in 

 the case of butter it is advisable to melt it in a closed vessel at 

 ^bout 40° C. (104° F.) and to shake violently till solid). Place 

 a few grammes in a small basin with a glass rod and weigh. 

 After adding acid, transfer, with the rod, from 1 to 2 grammes 

 (according to percentage of fat, 1 for butter, 1 '5 for clotted cream, 

 and 2 for cheese) ; add water to make up to 11 '22 grammes and 

 1 c.c. of amyl alcohol, and proceed as before. Calculate as for 

 sour milk. 



To Clean the Bottles. — After reading, place the bottles in the 

 stand, cork upwards ; take out the corks and wash them several 

 times with hot water. Do not use soda. Empty the bottles 

 into a suitable vessel and fill them with hot water ; empty this 

 out completely and repeat twice ; if not quite clean run a brush 

 down them and wash again. Invert the stand and let the bottles 

 ■ drain. Dry the corks after use. Never leave pipettes dirty. 



Keep the stopper in the sulphuric acid bottle when not in use. 



Gerber recommends a butyrometer with two openings for 

 solid products ; the lower cork carries a little glass cup of 1 c.c. 

 capacity, and the product to be tested is weighed into this. The 

 author has not found this advantageous. 



Cream and Clotted Cream. — Well mix from 60 to 100 grammes 

 of the sample to be tested, fill the cup with this, dry the outside 

 and weigh. Place the cork carrying the cup in the butyrometer, 

 add 6 c.c. of clear hot water through the upper opening, then 

 1 c.c. of amyl alcohol and 6-5 c.c. of acid, and shake well ; add 



