242 An Investigation of the Properties of Lactic Acid. 



which we usually derive the principal and the most certain 

 crilerions of an acid. They conchided from their experi- 

 ments, that Scheele had been mistaken, and that the lactic 

 acid was nothing else than a combination of the acetic with 

 a proper animal matter, which hindered the volatilisation of 

 the acid. 



Since we have found that the lactic acid acts a more or 

 less distinguished part in the blood, in muscular flesh, in 

 the marrow, in urine, and in milk, it appears desirable thal^ 

 these circumstances should be very accurately examined; 

 I have therefore undertaken to investigate its nature very 

 fully, and have obtained, by means of a long and often re- 

 peated series of different experiments, a complete conviction 

 that .Scheele was in the right, and that the lactic acid is a 

 peculiar acid, very distinct from all others. 



I shall here relate the results of my experiments. The 

 extract which is obtained when dried whey is digested with 

 alcohol, contains, as 1 have already observed, uncombined 

 'actic acid, lactate of potass, muriate of potass, and a pro- 

 per animal matter. I mixed this solution in alcohol with 

 another portion of alcohol to which -pij- of concentrated 

 sulphuric acid had been added, and continued to add fresh 

 portions of this mixture as long as any saline precipitate was 

 formed, and until the fluid had acquired a decidedly acid 

 taste. Somesulphateof potass was precipitated, and there re- 

 mained in the alcohol muriatic acid, lactic acid, sulphuric 

 acid, and a minute portion of phosphoric acid, detached 

 from some bone earth which had been held in solution. The 

 acid liquor was filtered, and afterwards digested with car- 

 bonate of lead, which with the lactic acid affords a salt so- 

 luble in alcohol. As soon as the mixture had acquired a 

 sv.-eetish taste, the three mineral acids had fallen down in 

 combination with the lead, and the lactic acid remained be- 

 hind, imperfectly saturated bv a portion of it, from which 

 it was detached by nieans of sulphuretted hydrogen, and 

 then evaporated to the consistence of a thick varnish, of a 

 dark-brown colour and sharp acid taste, but altogether 

 w itiioiit smell. 



In order to free it from the animal matter which might 

 feniain combined with it, I boiled it with a mixture of a 

 large quantity of fresh lime and water, so that the animal 

 5ab>fanccs were precipitated and destroyed bv the lime. 

 The lime became yellow brown, and the solution almost 

 colourless, while the mass emitted a smell of soap lees, 

 which disappeared as the boiling was continued. The fluid 

 thus obtained was filtered and evaporated; until a great part 



of 



