m 



as, on repeating the analysis of the compound, he found that he had 

 somewhat over-estimated the amount of bromine contained in it, 

 while its other constituents were determined correctly enough. 



Bettt'-orcine, 



This substance, described by the author in the Philosophical Ma- 

 gazine for July 184-8, may be obtained from usnic acid, either by 

 destructively distilling it, or by acting on it with alkalies. 



Beta-orcine crystallizes very beautifully in four-sided prisms sur- 

 mounted at either end by four-sided pyramids. These crystals have 

 a brilliant lustre, and are from three quarters of an inch to an inch 

 long. Their solution strikes a fugitive bright-red colour with hypo- 

 chlorite of lime, and with a solution of ammonia it yields a perma- 

 nent blood-red colouring matter which becomes darker on standing. 

 The formula of beta-orcine, which however is merely empirical, is 



Ci6 O4. 



Quintonitrated erythromannite. 



In his former paper on the lichens, the author has described, under 

 the name pseudo-orciiie, a remarkably beautiful crystalline body 

 which is obtained by boiling either picro-erythrine, or erythric acid, 

 with an excess of lime or baryta. This substance he then regarded 

 as very analogous to mannite both in its composition and properties, 

 and this view having been amply verified by an experiment which 

 he has recently made, he has been induced to change the name of 

 this compound to erythro-mannite, as at once indicating its origin 

 and its most striking properties. After referring to the discovery by 

 Messrs. Flores Domonte and Menard, of "Mannite quintonitrique" 

 or mannite in which five equivalents of water are replaced by five 

 equivalents of nitric acid, and which possesses the remarkable pro- 

 perty of detonating so violently when struck by a hammer that M. 

 Sobrero has proposed employing it, instead of fulminate of mercury, 

 in the manufacture of percussion-caps, the author states that when 

 erythro-mannite is treated v/ith fuming nitric acid, in exactly the 

 same way as mannite, it yields a perfectly analogous compound, or 

 erythro-mannite in which five equivalents of water are replaced by 

 five equivalents of nitric acid. This compound, which he has called 

 quintonitrated erythromannite, is also insoluble in water, but cry- 

 stallizes out of hot spirits in large flat crystals resembling those of 

 benzoic acid, only larger and exhibiting a much more pearly lustre. 

 Quintonitrated erythromannite also detonates with great violence 

 when it is mixed with a little dry sand, and is strongly struck with 

 a hammer. 



In order to exhibit more distinctly the close analogy which sub- 

 sists between the four compounds, their rational formulae are given, 

 viz. 



Mannite = C12 H14 O^o ; 



Erythro-mannite = Cn H14 0^ ; 



Quintonitrated mannite = C12 Hg O7 + 5NO5 ; 



Quintonitrated erythromannite = Cn Hg Og + SNO^. 



