170 



Mr. Perkin on Mauve or Aniline-Purple. [1864. 



I have now remedied this defect, and made what I beheve is an absolute 

 standard barometer, by graduating the scale from the centre, and reading 

 it off with two verniers to the j^^^th of an inch. The scale is divided 

 from the centre, up and down, into inches, and subdivided into 20ths. 



To ascertain the height of the barometer graduated in this way, take a 

 reading of the upper surface of the column of mercury with the vernier, 

 then of the lower surface in the same way, and the two readings added to- 

 gether will give the exact length of the column of mercury supported in the 

 air, which is the height of the barometer at the time. 



There is another advantage in this manner of graduating over the 

 former, that if a little of the mercury drops out it will give no error, as the 

 column will immediately rise out of the larger tube into the smaller, and 

 become the same length as before ; but by the former scale the barometer 

 would stand too high, until readjusted, which could only be effected by 

 putting the same quantity of mercury in again. 



I have introduced Gay-Lussac's pipette into the centre of the tube, to 

 prevent the possibility of any air passing up into the top. 



The Society then adjourned over the Easter Recess to Thursday, April 7th. 



'^On Mauve or Aniline-Purple.'' By W. H. Perkin, F.C.S. Com- 

 municated by Dr. Stenhouse. Received August 19, 1863*. 



The discovery of this colouring matter in 1856, and its introduction as a 

 commercial article, has originated that remarkable series of compounds 

 known as coal-tar colours, which have now become so numerous, and in 

 consequence of their adaptibility to the arts and manufactures are of such 

 great and increasing importance. The chemistry of mauve may appear to 

 have been rather neglected, its composition not having been established, 

 although it has formed the subject of several papers by continental chemists. 

 Its chemical nature also has not been generally known ; and to this fact 

 many of the discrepancies in the results of the different experimentalists 

 who have worked on this subject are to be attributed. 



The first analysis I made of this colouring matter was in 1856, soon 

 after I had become its fortunate discoverer. The product I examined was 

 purified as thoroughly as my knowledge of its properties then enabled me, 

 and the results f obtained agree very closely with those required for the 

 formula I now propose. Since that time I have often commenced the study 

 of this body in a scientific point of view, but other duties have prevented me 



* For abstract see vol. xii. p. 713. 



t The substance I examined was doubtless the sulphate, of which I made two com- 

 bustions : — 



No. T. gave 7r55 per cent, of carbon and 6*09 per cent, of hydrogen. 

 No. II. gave 71-60 „ „ 5-77 



Theory requires 71*5 „ „ 5*5 „ 



