ON MILK 199 



sensible, to which the whole phenomenon otherwise might 

 easily be ascribed. Here therefore a double decomposition 

 takes place, the alkali uniting with the muriatic acid, and 

 the principle of heat with the white of the eggs. If aerated 

 alkali be employed instead of the caustic in the same process, 

 no coagulation takes place. 



SECTION VII. 



It is a known fact that milk in a short time grows sour 

 and thick during the summer. This sourness daily increases, 

 and is the strongest after a fortnight has elapsed. If the 

 whey be then filtered and evaporated to one-half of its 

 quantity, a few curds settle to the bottom. If it be filtered 

 again, and a little acid of tartar be added, some time after- 

 wards a great number of small crystals are generated, which 

 fall to the bottom, and appear on examination to be tartar. 

 The origin of this tartar I cannot ascribe to the small 

 quantity of muriated vegetable alkali which the milk always 

 contains, for this salt exists in milk in too small a quantity 

 to produce any effect here ; it is rather to be ascribed to an 

 essential salt contained in the milk. This is further evident 

 from this, that when whey evaporated by itself to dry ness, 

 and afterwards reduced to charcoal in a crucible, by which 

 process this essential salt is destroyed, it is found that this 

 coal contains vegetable alkali, mixed with a little muriated 

 vegetable alkali, which may be obtained by lixiviation with 

 water. The whey also contains in solution a portion of 

 animal earth, as may be seen when it is saturated with 

 caustic volatile alkali, as also with lime-water. Thus the 

 acid of milk contains an essential salt, animal earth, sugar 

 of milk, a little muriated vegetable alkali, and some 



