278 



Researches on Lactin. 



[Jan. 23, 



larger quantity of acid were used, the first changes were so rapid as to 

 evade measurement ; moreover, the oxalic acid formed, by crystallizing 

 in the acid liquid, made accurate observation impossible. By adding 

 the acid in small successive portions, we nevertheless succeeded in 

 obtaining an outline of the reaction, of which the curve drawn below 

 is an accurate general expression. 



Hydrio Nitrate. 



Dubrunfaut, who has also examined this action,* asserts that the 

 rotatory power first rises to \^ of the original amount, then falls 

 gradually to zero, again rises to \ of the original rotation, and once 

 more falls to zero : the highest rotation corresponding to galactose, 

 the first point of inactivity to mucic acid ; the second rise probably to 

 dextro-tartaric acid ; and the second fall to the formation of oxalic 

 acid. Our experiments show the formation of a la3vo-rotatory sub- 

 stance, perhaps lsevo-tartaric acid. The general form of the curve 

 constitutes it an interesting and novel addition to chemical curves. 



V. Note on Solubility. — The mutual relations of water and lactin in 

 solution undergo a change upon which the change of rotation most 

 probably depends. Water shaken with a large quantity of very finely 

 powdered lactin at a temperature of 17° C, takes up a quantity of 

 lactin corresponding to a solubility of 1 part lactin in 10 - 64 parts 

 water. With four hours' contact, the solubility increases to 1 part 

 lactin in 7*49 parts water. The permanent solubility got by the 

 analysis of the mother-liquor of lactin crystallized over oil of vitriol is 

 1 part lactin in 3*23 parts water. In the solution of the lactin a fall 

 of temperature of 0°'45 C. was observed. Pohlf also found a de- 

 pression of temperature (0°'88 C.) ; while Dubrunfaut alleges that 

 heat is evolved. 



Conclusions. 



I. The initial specific rotation of lactin is 92°'63. 



II. The permanent specific rotation of lactin is 59° '17. 



* " Compt. rend.," xlii, 228. f " Journ. Pr. Cheni.," lxxxii, 154. 



