1823.] Mr. Crum on Indigo. 99 



and after two hours and a half, when quite blue, the mixture was 

 poured into a pint of water, and heated to boiling. It was then 

 thrown upon a weighed filter, and washed ; first with boiling 

 water, in which had been dissolved a minute portion of sulphate 

 of lime, and afterwards with boiling pure water. The purple 

 substance remaining upon the filter, when thoroughly dried, 

 weighed 9*61 grains ; a portion of which being burnt, left a 

 quantity of ashes, equal to 1*37 grain of the whole ; consequently 

 only 8*24 grains of pure phenicin had been produced. The 

 washings, which were deeply blue coloured from the cerulin that 

 had been formed, were put together ; and when diluted with 

 water to 95 cubic inches, exactly equalled in intensity a solution 

 of 1 grain of indigo converted into cerulin, in 30 inches of water. 

 Hence 3*16 grains of the indigo had been expended on the pro- 

 duction of cerulin, and 6*84 grains had produced 8*24 grains of 

 phenicin. 



In another experiment, 4*2 grains of indigo produced 5*13 

 grains of phenicin ; and in a third, 4*79 grains produced 5*65 

 grains. The mean of these makes 100 of indigo produce 120 of 

 phenicin. 



By analysis with peroxide of copper, I have obtained results 

 which indicate a smaller increase of weight ; and I am inclined 

 to prefer these to the synthetic result, because the phenicin 

 operated upon is much more pure, and the experiment altoge- 

 ther less liable to error. One grain of pure phenicin produced 

 5*085 cubic inches of dry carbonic acid gas, which contain 

 0*6462 grain of carbon. Hence, calculating as in the case of 

 cerulin, the substance consists of 



Carbon 64-62 



Azote 9-91 



Oxygen 21*49 



Hydrogen 3*98 



100*00 



This is very nearly indigo + 2 water, and its atomic propor- 

 tions may be thus stated : 



1 atom azote 1*75 or 946 



4 atoms oxygen 4*00 21*62 



6 atoms hydrogen 0*75 4*05 



16 atoms carbon 12*00 64*87 



18*50 100*00 



The experiments of Mr. Smithson, related in the Philosophical 

 Transactions, have given us very correct ideas on the nature of a 

 number of the vegetable colouring matters. It is sufficiently 

 obvious that phenicin is not the principle which colours any of 



n 2 



