MISCELLANY. 
265 
By these means a persistent rheumatic affection of the feet accompanied 
with swelling of the extremities and knees, was removed in a short time. 
Journal de Pharmacie. 
Indigo, Sulphindilic acid. Analogy between Alcohol and Indigo as 
regards their combination with sulphuric acid. — M. Dumas presented a 
memoir to the Institute, in which he states, that he has repeated the 
analysis of indigo, and has obtained exactly the same results as those 
obtained by him five years since. His analysis gives as the composition 
of indigo : — 
Carbon, 73.0 
Hydrogen, 4.0 
Azote, 10.8 
Oxygen, 12.2. 
The author has endeavoured to determine the nature of the compound 
formed by the reaction of sulphuric acid upon indigo. It is known that 
this acid has the power of dissolving indigo and becomes coloured blue in 
consequence of this solution. Berzelius considered this combination as 
a species of lacker. M. Dumas, on the contrary, regards it as a compound 
analogous to sulphovinic acid ; he names it on this account sulphindilic 
acid ; it results from the combination of two atoms of sulphuric acid with 
an atom of indigo. 
This acid forms with potassa a salt soluble in water, crystallizable in 
delicate silky needles, of a deep blue colour; it produces with baryta, 
a salt little soluble in cold, more so in warm water. 
From the analysis of these two salts, it lesults that the formula for 
indigo is, C^^ H^^ AZ^ 0% and that the sulphindilic acid ought to be 
represented by 2 S03+C32 H^^ AZ^ 02; by adding to this formula, an 
atom of bas, that of the sulphindilates is obtained. It is known that 
when indigo is treated with sulphuric acid, a purple substance is often 
formed, very difficult to be separated from the blue matter. M. Dumas 
calls this combination sulphopurpuric acid; it is represented by two atoms 
of indigo and two atoms of sulphuric acid, or of sulphindic acid, plus an 
atom of indigo. It forms with potassa a purple salt, soluble in water. 
White Indigo. — M. Dumas has analyzed the white matter into which in- 
digo is transformed, when submitted to the action of alkalies and reductives; 
he has found in it the same composition as in indigo itself, with the 
difference of nearly two atoms of hydrogen which white indigo contains 
in addition. Hence it is a hyduret of indigo, and not indigo deoxygenized 
as is generally believed. 
Anilic Acid. — This name has been bestowed by M. Dumas upon an 
acid formerly called indigotic, obtained by the reaction between nitric acid 
