and on the Nature of the Diamond. 323 



constantly varying, and evtn the most beautiful theories are 

 liable to change. 

 The experiments above related give us the following results -. 



By carbonic acid. By oxygen- 



Box-wood charcoal 28-92 £8-77 



1st expt. diamond £8-95 25-81 



2d expt. diamond 28*82 28-72 



Stone coal - 28-20 28-27 



Plumbaso - 28-46 28-46 



5)143-35 5)143-03 



28-67 ♦28-60 



Hence we conclude that 100 grains of carbonic acid con- 

 tains 2S-60 of carbon, which does not greatly differ from 

 the results of the experiments of Smithson Tennant, escj. 

 on the nature of diamond. — See Phil. Trans. 1797. 



This gentleman made his experiment in the following 

 manner : A quarter of an ounce of nitrate of potash was 

 rendered somewhat alkaline by exposure to heat, in order 

 that it might more re:'.dily absorb carbonic acid ; it was then 

 put into a gold tube with 2t grains of diamond ; and being 

 subjected to heat, the diamond was converted into carbonic 

 acid, by uniting with the oxygen contained in tlie nitric 

 acid. The carbonic acid thus produced combined wiih the 

 potash ; and on pouring a solution of n.uriate of lime into a 

 solution of this salt, he obtained a precipitate of carbonate 

 of lime: this being decomposed by muriatic acid, gave as 

 much carbonic acid gas as occupied the space of 10-1 ounces 

 of water. The ihermometer was at bb'^ Fahrenheit, the ba- 

 rometer 29-80. In a second experiment he procured a 

 larger quantity, or equal to 10-3 ounces of water. 



If we therefore consider an ounce of water as coiisistnio^ 

 of 460 grain?, and a cubic inch of water equal to 233 grains, 

 and then make the proper corrections for tempeviMure and 

 pressure, one of his experiments will give about 27 per cent. 

 the other about 27-6O for the carbon in carbonic acid, which 

 is somewhat less than our estimate; but llie difi'crjuce may 

 easilv be accounted for, from the different methods cmplovcdf 



X 2 The 



