GERBER METHOD. 239 



6 c.c. more hot water, shake again and whirl in the machine. 

 Read after one minute's standing in the water-bath. 



Butter. — ilelt about 10 to 20 grammes in a small closed bottle 

 at 40^ C. (104° F.) and shake violently till solid; fill the cup, 

 and weigh. Add 12 c.c. of cold water, and 1 c.c. of amyl alcohol 

 and 6 5 c.c. of acid. Shake well and proceed as before. 



Clierse. — Mix 10 to 20 grammes in a mortar till of even con- 

 sistency. Fill the cup and weigh ; transfer the bulk of the 

 cheese from the cup to the butyrometer, by inserting the cork 

 and shaking gently ; add 6 c.c. of hot water and 6"5 c.c. of acid 

 and shake till the cheese is dissolved. Now add 7 c.c. of hot 

 water and 5 drops of amyl alcohol (from the pipette), shake well 

 and whirl in the machine. Stop the machine after about two 

 to three minutes, take out the butyrometer, add a further 1 c.c. 

 of amyl alcohol, and place for a minute in the water-bath at 

 60' to 70° (say 150° to 160° F.) ; whirl again and read after a 

 minute's standing in the water-bath. 



For Skim Chrescs whirl three times and add 8 c.c. of hot water 

 instead of 7 c.c. 



(Calculation of Results. — The percentage of fat in the sample 

 is found by dividing the number of degrees read off on the stem 

 of the butyrometer by the weight taken, thus 



G'2 

 Butter wt. 0'76 gramme. Reading 62° Fat = -— = SI -6 per cent. 



49 



Oeam wt. 090 ,, ,, 49° ,. = —^ = o4'4 



Cheese wt. -68 ,, ,, 22" ,, = -Ij^;^ = 32-35 ,, 



Water Estimation in Butter, Margarine, ete. — A special form of 

 butyrometer is used for this ; it consists of an elongated bulb 

 5 c.c. in capacity, connected by a graduated tube with a vessel 

 in which a cork carrying a cup of 3 c.c. capacity is inserted. 

 The only reagent necessary is diluted sulphuric acid, made by 

 diluting commercial sulphuric acid (sp. gr. 1820 to 1"825) with 

 an equal bulk of water ; before use this should be cooled to the 

 ordinary temperature, and decanted from any deposit of lead 

 sulphate. 



Five c.c. of diluted sulphuric acid are measured into the buty- 

 rometer, which is placed open in the machine, and whirled for 

 about two minutes, in order to brini; all the liquid into the bulb ; 

 the level of the acid (at as near 60' F. (15'5° C.) as possible) is 

 read off on the graduated scale. About 2i to 3 grammes of 

 butter are weighed into the cup, and after the cork has been 

 inserted, the butyrometer is stood in the water-bath at 60° to 

 TO- C. (say 15(r to 160° F.) to melt the butter; when this has 



