MISCELLANY. 
79 
.hydrogen, and a reciprocal decomposition of this sulphuretted hydro- 
gen and the sulphurous acid into water and sulphur. 
If phosphorous acid be mixed with a solution of sulphurous acid in - 
water and heated, an abundant precipitate of sulphur is immediately 
formed. It is a very good means of discovering whether phosphoric 
acid contains phosphorous acid, as is often the case : if it contains ar- 
senious acid at the same time, it turns yellow on the precipitation of 
sulphuret of arsenic. 
The presence of phosphorous acid is very easily detected by means 
of a small gas apparatus, similar, to Marsh's. Indeed, if phosphoric 
acid containing phosphorous acid be mixed with a liquid disengaging 
hydrogen gas, phosphoretted hydrogen is formed, which may be re- 
cognized by its smell alone; and if this gas be inflamed, it burns with 
a whitish, brilliant flame, very different from that of pure hydrogen gas. 
If this flame be directed against a porcelain plate, there is always re- 
marked, and in a very evident manner, especially if the place be not 
too light, a circle of green light in the flame thus spread out, as when 
phosphorous burns in confined air or in chlorine. 
Chemist, from Journ. dt Pharm. 
Crystals of the Essences of Turpentine and Citron. By M. Deville. — 
M. Deville presented to the Philomatic Society of Paris, at its meet- 
ing of the 27th of November, 1841, two new products which he had 
recently obtained under the form of crystals, remarkable for theirbeauty, 
transparency, and lustre. 
The first was hydrated essence of turpentine, and the second, essence 
of citron. 
He read the following observations on this subject ; — 
Mr.Wiggers announced that he had obtained fine crystals of the former 
substance by means of a mixture of alcohol, nitric acid, and essence of 
turpentine. I have repeated this experiment, which perfectly succeeded, 
and I obtained two or three hundred grammes of substance at the end 
of a month of contact between two kilogrammes of the mixture. In an 
analogous manner, I was able to prepare the hydrated essence of citron, 
not previously known. 
These two substances crystallise with remarkable distinctness. 
They are isomorphous, and their forms are right rectangular prisms. 
They are likewise isomeric, and their formula is C4o H32-|_Hi2 
06, a formula which Dumas and Peligot had already assigned to hy- 
drated essence of turpentine. 
It appeared to me that there should also exist a liquid hydrate of the 
two essences. 
