Jan. 1, 1865.] THE TECHNOLOGIST. 



ON CHEMISTRY APPLIED TO THE ARTS. 281 



When whey is concentrated to the state of syrup and kept in a cold 

 place, it gradually deposits fine, well-defined crystals, which, on further 

 purification and re-crystallisation, yield white quadrangular prisms of a 

 substance called lactine, or sugar of milk, which is highly interesting. It 

 is remarkable that while sugar of milk has only been known in Europe 

 for a comparatively short period, where homceopathists are its principal 

 employers, in India lactine has been known for a great number of years. 

 Let us now study some of the chemical facts connected with sugar of 

 milk. Thus cane sugar, when acted upon by nitric acid, gives oxalic 

 acid, whilst lactine gives mucic acid ; cane sugar, when unfolded under 

 the influence of a ferment, gives alcohol and carbonic acid ; lactine 

 yields lactic acid. As the latter transformation is most important, in a 

 physiological and chemical point of view, allow me to dwell upon it for 

 a few minutes. The substance which possesses the property of most 

 readily converting lactine into lactic acid is caseine after it has under- 

 gone some peculiar modification, which renders it a ferment. Thus 

 when milk leaves the cow it is alkaline, but when exposed to the air it 

 rapidly becomes acid, and this is due to the conversion of lactine into 

 lactic acid, a change most interesting as a chemical fact, since both lac- 

 tine and lactic acid have the same composition, the oniy difference 

 being that two equivalents of oxygen and two of hydrogen cease to exist 

 as such in the acid, but may be considered as combined in the form of 

 water with the remaining elements — 



Lactine C 12 H 13 12 = 2 Lactic acid (C e H 6 5 HO). 



M. Pasteur has shown that this lactic fermentation is not merely 

 confined to milk, but that it is a peculiar fermentation, differing from 

 the previous one, which frequently occurs during the decomposition of 

 organic matters, and is due to a distinct ferment of its own ; and his 

 researches on lactic fermentation have explained the fact, observed by 

 M. Pelouze, some years since, that when a vegetable substance, such as 

 sugar or starch, was put in contact with chalk or other alkali and an 

 animal substance, lactic fermentation ensued, but until the researches of 

 M. Pasteur, we did not know why sugar and starch in these circum- 

 stances should give lactic acid instead of alcohol and carbonic acid, 

 which would be the result of a fermentation produced by yeast. Lactic 

 acid is a most interesting substance to the physiologist, for it is found 

 in large quantities, free or combined with lime, in gastric juice, in the 

 muscular part of animals, or with soda, in blood, and its production is 

 easily accounted for when we remember that it can be produced from the 

 starch and sugar existing in our food. When lactic acid is purified by 

 various chemical means and separated from the fluid in which it is combined, 

 it presents itself as a syrupy fluid, of an intensely acid reaction, which, 

 when submitted to the action of heat, first loses its one equivalent of 

 water, and becomes anhydrous lactic acid, and on a further application 

 of heat loses still one equivalent of water, and is transformed into a 



