202 AGRICULTURAL PRODUCTS. [VIII. 



lbs. oz. 



Phosphoric acid 27 ... 14| 



Sulphuric " ... 13| 



Potassa ...* 11 ... 4 



Soda 4 ... 10 



Chloride of sodium ... T 



Lime 18 ... 14 



Magnesia 4 ... 1 



Silicic acid ... 5 



68 5 



6. Agricultural Products. — That chemistry might prove a 

 great benefit to agriculture, no one doubts ; but that it has not 

 yet done so, is true. The changes undergone by milk and 

 cream in their metamorphosis into cheese and butter have not 

 been minutely and accurately studied ; and by way of illus- 

 trating the bearing of chemistry on these points, we offer an 

 alkalimetric method of determining the richness of milk, and 

 Reiset's examination of the yield of butter under different cir- 

 cumstances of milking. 



Lactometry. — Poggiale (Comptes Rendus, 1849) proposes to 

 estimate the richness of milk by determining the volume of 

 sugar of milk contained in it ; the proportion of that in- 

 gredient having been found by experiment to be uniformly 

 near 52.7 in 1000 pts. of pure milk. His process is based 

 upon the reduction of copper-salt by sugar of milk. He 

 employs a test-liquid, made by mixing a solution of 10 grm. 

 crystallized sulphate of copper, with one of 10 grm. crys- 

 tallized bitartrate of potassa, and dissolving the precipitate in 

 an aqueous solution of 30 grm. caustic potassa, diluting with 

 water to the quantity of 200 grm., and filtering. 20 cubic 

 centimeters of this clear blue liquid correspond with two 

 decigrammes of whey, of which latter pure milk contains 923 

 pts. in the thousand. In 1000 pts. of whey, there are there- 

 fore 57 pts. of sugar. The fat and casein having been 

 coagulated by mixing the milk, say 50 grm. with a few drops 

 of acetic acid, and heating to 120°, are then to be separated 



