1872.] Colouring -matters from Aromatic Azodiamines. 57 



produced on the large scale; the last was prepared by M. Grirard 

 himself. 



Safranine occurs in commerce either as a solid body or en pate. In 

 the solid state it forms a yellowish-red powder, in which, together with 

 considerable quantities of chalk and common salt, the chlorhydrate of 

 a tinctorial base may be recognized. The pure dye is easily sepa- 

 rated from crude safranine. It is only necessary to exhaust the com- 

 mercial product with boiling water ; on cooling, the nitrate deposits 

 a slightly crystalline substance which, after several recrystallizations 

 from boiling water, leaves no residue on ignition. During these opera- 

 tions, however, the salt undergoes perceptible alteration ; with every 

 recrystallization it becomes more soluble and less crystalline. These 

 alterations depend upon the separation of chlorhydric acid from the salt. 

 In fact the percentage of chlorine is found to diminish in the product of 

 successive crystallizations ; thus the product of the third contained 8*48 

 per cent., that of the fourth crystallization only 7*46 per cent. Addi- 

 tion of chlorhydric acid to the mother-liquors at once reproduces a 

 crystalline precipitate. This instability of the chlorhydrate, and in fact, 

 as may even now be stated, of the salts of safranine in general, has very 

 considerably impeded the study of this body, and often materially affected 

 the accuracy of the analytical results. In order to obtain the normal 

 salt, the boiling liquid during the last crystallization had always to be 

 acidified with chlorhydric acid. 



Safranine chlorhydrate separates in fine reddish crystals from the acid 

 solution on cooling ; an appreciable quantity of the compound, however, 

 remains in solution. The salt dissolves both in water and alcohol, more 

 readily when hot than when cold ; it is insoluble in ether, as also in con- 

 centrated saline solutions. The alcoholic solution, like the aqueous, is of 

 a deep reddish-yellow colour ; it exhibits a peculiar fluorescence, which in 

 a measure recalls that of Magdala-red. Ether precipitates the salt from 

 the alcoholic solution. Numerous analyses which we have made of 

 this salt lead to the following two formulas : — 



the theoretical values of which agree almost equally well with the averages 

 of the experimental numbers. We were doubtful at first to which of 

 these two formulas preference should be given. Indeed the assumption 

 of twenty atoms of carbon in the molecule of safranine had its seductions ; 

 however, the values of the second formula agree perhaps somewhat better 

 with the results of analysis. Indeed we found invariably somewhat less 

 nitrogen than the quantity required by the former formula, whilst it is 

 well known that the volumetric method invariably gives an excess ; so that 

 we should have adopted the second formula, even if later experiments on 

 the preparation of safranine had not altogether excluded the former one. 

 Platinum salt of safranine. — The numbers obtained in the analvsis of 



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