1886.] 



Proteid Substances in Latex. 



33 



acid or alkaline, however, it behaved differently. In a nitric acid 

 solution an opalescence was noticeable when the temperature had 

 risen to 85 — 90° C. This was not removed by the addition of more 

 nitric acid. On keeping the vessel for some time at this temperature, 

 the opalescence became a precipitate, which was soluble at ordinary 

 temperatures in alkalis, slightly so in water, but not in nitric acid. 

 The solutions gave the xanthoproteic reaction. A curious point about 

 this body was the slowness with which the precipitate formed, it 

 appearing not at all like the usual conversion into coagulated proteid 

 on a rise of temperature, but more like a slow precipitation by the 

 reagent at that particular point. This was confirmed by several ex- 

 periments, one of which, often repeated, was the following. A 

 quantity of the extract was made acid with nitric acid and warmed 

 to 75° C, a point considerably below that at which the precipitate was 

 first observed to form. It was then allowed to cool, and as the tem- 

 perature was gradually falling, the precipitate slowly separated out. 

 The body seemed then to be slowly precipitated by nitric acid, but 

 not at the ordinary temperature. 



In an alkaline solution its behaviour was somewhat different. The 

 opalescence set in at 79° 0., and a bulky precipitate settled out slowly 

 at 85° G. This was soluble to a large extent in nitric acid, and was 

 reprecipitated when the liquid was made alkaline. A solution in 

 caustic soda of the precipitate caused by nitric acid at 85° C. behaved 

 similarly. The precipitation here also seemed to be caused by the 

 reagent and not by the temperature, for the alkaline liquid deposited 

 the proteid body on cooling just as the acid one did, and in about the 

 same time as when the temperature was kept constant at 85° C. 

 Both precipitates were unaltered in the separation; each went into 

 solution readily in its appropriate medium, the solutions all giving 

 the xanthoproteic reaction. 



This proteid gave no precipitate with acetic acid and potassic ferro- 

 cyanide. 



After removal of this body by repeated boiling and filtration, the 

 clear fluid gave a good xanthoproteic reaction. On applying some of 

 the tests used in the case of the East Indian latex, the same peptone- 

 like body was found to be present. It dialysed readily, and the 

 solution in water gave a precipitate on saturation with solid MgS0 4 . 



Hence it appears that the latex of Mimusops globosa contains two 

 proteids, one a member of the albumose group, precipitated under 

 certain conditions by nitric acid or by potash, but not by boiling, and 

 the other more nearly related to the peptones. 



In 1823, Boussingault and Mariano de Rivero* published some ob- 

 servations on the latex of the cowtree of South America (Brosimum 



* "Memoire sur le Lait de l'Arbre de la Yache (Palo de Vaca)," "Annales de 

 Clumie et de Physique," t. xxiii, 1823, p. 219. 



VOL. XL. D 



