148 hitelligence and Miscellaneous Articles. 



ON OXYPICRIC ACID. — STYPHNIC ACID. 



In experimenting on Indian yellow, M. Erdmann discovered a new 

 acid, to which he gave the name of oxypicric acid. 



This substance has also been obtained by MM. Boettgerand Will, 

 without their being aware of the results of M. Erdmann's experi- 

 ments. It was procured by these chemists by treating several gum- 

 resins with nitric acid, as for example ammoniacum, assafcetida, &c. ; 

 they also procured it from the watery extract of Brazil wood, San- 

 ders and yellow wood, and they have called it styphnic acid, from 

 arvipios, astringent . 



They prepare it by heating one part of assafcetida with from four to 

 six parts of nitric acid of r20. At first they heat it to about 158° 

 to 1 63° F. ; as soon as the violent action which then takes i)lace is 

 moderated, it is to be boiled till all solid matter disappears. When 

 the solution, on the addition of water, deposits a powder which is 

 granular to the touch, the oxidation is finished ; if the water sepa- 

 rates a flocculent precipitate, the ebullition with the nitric acid must 

 be continued : it is then to be evaporated to the consistence of a syrup, 

 much water is to be added, and after having boiled it, carbonate of 

 potash is to be added as long as effervescence ensues, taking care to 

 add no excess, in order that the resinous portions which the liquor 

 may still contain be not dissolved. After neutralization the liquor 

 is to be filtered and evaporated, and set to crystallize. There then 

 separates a salt of potash which is very slightly soluble, having the 

 form of a brown crust, or of fine needles aggregated in mammillated 

 forms. This salt is to be dissolved and re-crystallized in water, and 

 the oxypicric acid is to be precipitated by nitric acid. 



This acid is precipitated in the state of a white powder, or in scales 

 having the form of fern leaves ; it is to be washed with cold water 

 and then dissolved in boiling absolute alcohol ; from this it separates 

 in prismatic crystals of considerable size. 



The properties of this acid are that its taste is neither sour nor 

 bitter, but slightly astringent ; its solution, either in alcohol or water, 

 colours the epidermis permanently. 



It is yellow, reddens litmus strongly, and readily decomposes the 

 alkaline carbonates. It requires 88 parts of water at about 144° F. 

 for solution : alcohol and aether dissolve it readily. When cautiously 

 heated on platina foil it fuses, and on cooling becomes a radiated 

 mass : at a higher temperature it yields vapours which readily in- 

 flame. When suddenly heated it detonates slightly. 



Nitric and hydrochloric acids even when concentrated do not act 

 upon it at a boiling heat. It dissolves readily in concentrated nitric 

 acid, and water jjrecipitates it from solution in the form of a white 

 powder. 



Aqua regia decomposes it entirely with the production of oxalic 

 acid. Concentrated sulphuric acid when heated also decomposes it. 

 If a piece of very dry potassium be sprinkled with this acid, and it 

 be slightly pressed with a pestle, the acid inflames : sodium does not 

 produce the same eft'ect. 



A concentrated aqueous solution of oxypicric acid, especially when 



