GRRBER CREAM TESTING. 147 



Creams containing more than 32 per cent, of fat must be 

 diluted. Take two beakers or tin pots and counterbalance 

 them on a rough balance turning to 0-01 gramme, pour about 

 25 grammes of cream into one and add separated milk or water 

 to the other till the weights are equal, mix the cream and sepa- 

 rated milk or water, and measure as before. Use column 3 for 

 calculating the results. 



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. Mix the sample well 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. 



Calculate : Fat in sour milk = reading X -, . 



wt. taken 



Aii 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. Mix the sample well 

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

 about 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. 



