240 THE CHEMICAL CONTROL OF THE DAIRY. 



been accomplished, the whole is well shaken till the contents 

 form a uniform emulsion ; after standing for a minute in the 

 water-bath, the butyrometer is placed in the machine, and 

 whirled three times, warming in the water-bath for about two 

 minutes between each ; after the third whirling, it is cooled to 

 as near 60° P. as possible, and the level of the aqueous liquid 

 where it joins the fatty layer is read off. The difierence between 

 this reading and the level of the acid will give the percentage of 

 water if exactly 3 grammes of butter have been taken ; should 

 any other weight have been taken it is necessary to multiply 

 the result by 3 and divide by the weight taken ; thus, in an 

 experiment 2'780 grammes of butter were taken, the level of 

 the acid was 2"5° and the level of the aqueous liquid 14"5° ; the 

 percentage of water indicated is, therefore, 



(14-5 -2-5) X 3 12 X 3 ,,.„ 



2^ -* -' = -2^80' = ^^'^^ P^^ ^""*- '^^^'■ 



For the convenience of weighing out the cream, butter, etc., 

 in the cups, a balance of the steel-yard type can be obtained with 

 the machine ; it consists of a beam, with suitable supports, one 

 end of which is longer than the other ; from the shorter end, 

 which also carries a pointer, a small wire cradle to support the 

 cup is hung ; the longer end is divided into 10 equal parts, each 

 being indicated by a notch numbered 1 to 10 ; at the end of this 

 is a fine screw carrying a counterpoise, which can be moved 

 backwards or forwards by screwing round. 



The weighing is accomphshed by placing the cup in the cradle, 

 and screwing the counterpoise backward or forwards, as required, 

 till the pointer is at zero in the middle of the scale ; the cup is 

 now removed and filled with the product to be tested, and the 

 riders are put on the various notches in the beam in succession 

 till equilibrium is restored. The largest rider indicates grammes, 

 the medium tenths of a gramme, and the smallest hundredths 

 of a gramme. 



Thus if the largest rider is in notch 2, the medium 7, and the 

 smallest 8, the weight is 2 '780. 



If it be found that to restore equilibrium it is necessary to 

 place the smallest rider intermediate between two notches, say 

 between 2 and 3, the reading is taken as 0"025. 



If it be found that two riders must be placed on the same 

 notch to restore equilibrium, the smaller should be hung from 

 the upturned end of the larger. 



The use of this balance, though convenient when many samples 

 are being tested, is not necessary, as the weighings may be made, 

 but slightly less expeditiously, with an ordinary balance. 



Stokes' Modlflcatlon. — Stokes employs a modification of the 



