Black Substance from Sulphuric Acid a7id Alcohol. 277 



effected in vacuo at 130°-150° C. It does not decompose even 

 at 1 70° C. Hess's apparatus was employed for the analysis. 

 The substance was placed in a weighed glass capsule of the 

 form of a boat, this fixed in the tube between two coils of fine 

 platinum wire to prevent its coming into contact with the 

 oxide of copper, so that the weight of the incombustible re- 

 sidue might be determined. Between the tube containing 

 the chloride of calcium and the apparatus for the potassa, 

 a tube with oxide of lead was inserted, but no sulphurous 

 acid appeared to be formed. To determine the sulphuric acid 

 the substance was burnt with a mixture of nitre and carbonate 

 of soda. Mean of the experiments C 66-1 1, H 3-78, S 8*92, 

 O 21*19. It was then prepared according to the method em- 

 ployed by M. Lose, by passing alcoholic vapours into heated 

 fuming sulphuric acid, and purified as above. The product 

 was similar, and likewise left an incombustible residue, which 

 was determined in the same manner. The analysis gave 

 C 64-30, H 3-33, S 7-49, O 2'i-88. It was further prepared 

 by boiling pure distilled sulphuric acid with alcohol ; when 

 the mass began to thicken from the formation of the coaly sub- 

 stance, the experiment was interrupted and a portion was re- 

 moved, and cleaned by boiling with ammonia and water; the 

 second portion was so long exposed to a temperature of 180° C. 

 till the evolved gas was no longer combustible, and appeared 

 to consist solely of sulphurous and carbonic acids ; it was then 

 washed and dried. Both products had the same appearance, 

 and were subjected to analysis, the mean of which = C QS'SS^ 

 H i--55, S 8-38, 21-49. 



On treating the substances which had been employed in 

 the preceding experiments with a solution of caustic potash, 

 they ail evolved such considerable quantities of ammonia that 

 this could only be regarded as adhering mechanically to them. 

 The treatment with potassa was continued at the boiling point 

 till no smell of ammonia was perceptible, and the residues were 

 then washed with boiling water. On combustion they now 

 left considerable quantities of sulphate of potash. The black 

 substance can therefore combine with bases, and the residue 

 found by Erdmann in his previous analyses of the substance, 

 which had been treated with potash to remove the sulphuric 

 acid, was evidently sulphate of potash. Although the ana- 

 lyses communicated were made with ammoniaferous products, 

 and cannot consequently give the correct composition of 

 the black acid, yet as they liad all been treated in the same 

 way with an excess of ammonia they should evince a coinci- 

 dence did the black substances possess a constant composi- 

 tion. But this is not the case. The products obtained by 



