1872.] Colouring-matters from Aromatic Azodiamines. 59 

 The analysis of the nitrate, dried at 100°, leads to the formula 



Safranine picrate. — We have finally investigated the picrate. It is 

 obtained by simply adding an aqueous solution of picric acid to the 

 mother-liquors of the chlorhydrate or nitrate, and washing the precipitate 

 thus formed with water. The picrate forms red-brown needles, which 

 are insoluble in water, alcohol, and ether. 



Analysis gave results corresponding to those obtained in the in- 

 vestigation of the chlorhydrate, the platinum salt, and the nitrate, and 

 leading to the formula 



C 27 H 23 N 7 O,=C 21 H 20 N 4 . C 6 H 3 (N0 2 ),0. 



We have no further analytical data to offer at present. A brief notice of 

 several other salts we have prepared may, however, still be appended. 



Safranine bromhydrate is deposited on addition of bromhydric acid to a 

 solution of the base as a crystalline powder, consisting of microscopic 

 needles, which are so insoluble in water that the liquid from which they 

 have been precipitated appears almost colourless. The salt is soluble in 

 boiling water, from which it crystallizes on cooling. It is worth men- 

 tioning that, on adding bromine water to a solution of the chlorhydrate, 

 a red crystalline precipitate is formed, which is difficultly soluble in cold 

 water, but may recrystallize from boiling water. In this way needle- 

 shaped crystals are obtained which, when pure, possess a green metallic 

 lustre. They have not yet been analyzed. 



The iodhydrate, as regards preparation and properties, is perfectly 

 similar to the bromhydrate. 



The sulphate of safranine is a rather soluble salt ; only in the most 

 concentrated aqueous solution of the base is a precipitate prcduced on 

 addition of dilute sulphuric acid ; the salt dissolves on heating the liquid, 

 and is again deposited on cooling in the form of fine needles. 



The oxalate behaves very similarly, but is a little less soluble than the 

 sulphate ; with acetic acid the base gives no precipitate ; by spontaneous 

 evaporation the acetate separates in rather indistinct crystals. 



All the salts of safranine exhibit a very characteristic reaction; on 

 adding chlorhydric or sulphuric acid to the solution of the salt, the 

 red-brown colour of the liquid changes to a beautiful violet, which, on 

 addition of more acid, becomes a deep blue, then a dark green, and finally 

 a bright green ; if the acid liquid be slowly diluted with water, these 

 changes of colour may be observed in inverse order. 



It need scarcely be mentioned that in the course of this investigation 

 our attention has been repeatedly directed towards the preparation of 

 safranine ; it may, however, at once be stated that our experiments on 

 this subject have yielded but scanty results. As yet but little is known 

 regarding the preparation of safranine on a large scale. According to a 



