405 



chalk, gave no indications of sugar. Sugar, however, together with 

 a good deal of mucilage and resinous matter, with some larixinic acid, 

 is contained in the crude decoction of larch-bark. 



Bark of the common black Mangrove (Rhizophora Mangle of bota- 

 nists}. This species of mangrove-bark is used in tanning, and is 

 occasionally imported into Great Britain for this purpose. It has a 

 brownish-red colour : the colour of its decoction is the same. The 

 tannin it contains is precipitated from its solution both by acetate of 

 lead and concentrated sulphuric acid. When boiled with dilute sul- 

 phuric acid no sugar is produced, and the brownish-red precipitate 

 which falls cannot be made to crystallize. 



In conclusion, I would observe that it is somewhat remarkable 

 that so many of the tannins which give bluish-black precipitates with 

 persalts of iron are glucosides ; whereas of those which give olive- 

 green precipitates with persalts of iron, so far as I know, only one 

 to wit, the tannin of the willow is a glucoside. 



II. " On Larixinic Acid, a crystallizable volatile principle found 

 in the Bark of the Larch Tree (Pinus Larix, Linn.)." By 

 JOHN STENHOUSE, LL.D., F.R.S., F.C.S. Received July 

 10, 1861. 



(Abstract.) 



This acid is prepared by digesting larch-bark in water at 80 C., 

 evaporating the infusion at the same temperature to the consistence 

 of syrup, and distilling it in vessels of glass, porcelain, or silver ; 

 i. e. of a material not liable to be attacked by the acetic acid present 

 in the infusion. The larixinic acid distils over, and partly crystal- 

 lizes on the inner surface of the receiver, but chiefly remains dis- 

 solved in the distilled liquid, which, after being concentrated by 

 cautious evaporation, deposits the impure acid in form of crystals. 

 These are of a brownish-yellow colour ; they are to be dissolved 

 and recrystallized, and may be obtained quite pure by sublimation, 

 which takes place at the low temperature of 93 C. 



This acid exists as a proximate principle in the larch-bark ; most 

 abundantly in that from trees of not more than 20 or 30 years' 

 growth, or from the smaller branches of older trees. When pure, it 

 forms beautifully white crystals, often more than an inch long, of a 



