144 



VOLUMETRIC AND INDIRECT ESTIMATION OF FAT. 



Chemicals. Commercial sulphuric acid, specific gravity of 

 1-820 to 1-825 at 15 C. (59 F.) (contains 90 to 91 per cent. 

 H 2 S0 4 ). The specific gravity may be taken with a hydrometer. 

 Should the temperature not be exactly 15 C. (59 F.) the specific 

 gravity may be corrected by adding on 0-001 for each degree 

 Centigrade (or 0-00056 for each degree Fahrenheit above 59) 

 above 15, and by subtracting 0-001 for each degree below 15 ; 

 thus, if the temperature be 20 and the specific gravity 1-818, 

 the corrected specific gravity will be 1-818 + 5 X 0-001 = 1-823 ; 

 and if the temperature be 11 and the specific gravity 1-827, the 

 corrected specific gravity will be 1-827 4 X 0-001 = 1-823. 



Pure amyl alcohol specific gravity, 0-8165 to 0-818 at 15 

 (59 F.) ; boiling point, 124 to 130 C. should give a clear 

 solution with an equal volume of strong hydrochloric acid. 



Amyl alcohol sometimes contains petroleum, due to the use 

 of empty petroleum barrels as packages. A blank test with the 

 Gerber method fails to reveal the presence of petroleum if the 

 quantity is below 2 per cent., a quantity which gives an error of 

 about 0-2 per cent, in the fat estimation. 



It may be detected by running 10 c.c. of sulphuric acid, 10 c.c. 

 of water, and 2 c.c. of amyl alcohol into a Gerber butyrometer, 

 mixing and centrifuging ; no layer should appear if the amyl 

 alcohol be free from petroleum. If present an approximate 

 estimation of the quantity may be made ; the following results 

 were obtained by the author and Goodson : 



TABLE XXV. 



It is advisable to have a bottle of ammonia handy in case acid 

 is spilt on the clothes ; should this happen an application of a 

 few drops of ammonia at once will prevent damage. 



If strong acid is spilt on the skin, wash copiously with cold 

 water without delay and the white swellings formed will soon 

 disappear. 



Mode of Operation. 



Milk, Skim Milk, Whey and Buttermilk. Place a 



sufficient number of acido-butyrometers in the stand, open end 



