Some Experiments en the Comlust'ion of the Diamoud. 431 



of tlie Academia Lvncei. In the first series I was honoured by 

 tl^ie assistance of the Count Bardi, the Director, and Signior 

 Gazzari, the Professor of Cliemistrv at tlie Florentine Museum: 

 and in the last by that of Sig. Morrichini and Barlocci, Pro- 

 fessois of the College Sapienza at Rome. 



In the very-first trials on the combustion of the diamond, I 

 ascertained a circumstance that I believe has not been noticed 

 betore ; namely, that the diamond, when strongly ignited by the 

 lens in a thin capsule of platinum perforated wi\h' many orifices, 

 •so as to admit a free circulation of air, continues to burn in oxy- 

 gen gas after being withdrawn from tlie focus. The light "it 

 affords is steady, and of so brilliant a red, as to be visible hi the 

 brightest sunshine ; and tlie heat produced is so great, that in 

 one experiment, in which tliree fragments of diamonds weighing 

 1-M grain only were burnt, a fine wire of platinum used for at- 

 taching them to the tray was fused, RTid that some time after the 

 aiamonds were removed out of the focus. 



The knowledge of this circumstance enabled me to adopt a 

 very simple apparatus and mode of operation in my researches, 

 and to complete, in a few minutes, experiments which have been 

 suppo«;ed to rcnuire the presence of a bright sunshine for many 

 hours. ' ' 



My apparatus consisted of clear glass globes of the capacity 

 of from fourteen to forty cubical inches, having single apertures 

 to which stop- cocks were attached : a small hollow cylinder of 

 platiiiuni, which I use in experiments with the blow-pipe, was 

 attached to one end of the stop-cock, and was mounted with a 

 little perforated capsule of platinum for containing the diamond. 

 When the experiment was to be made, the globe containing tlie 

 capsule and the substance to be burned was exhausted by an ex- 

 cellent air-pump, and pure oxygen gas, made from hvpcroxy- 

 muriate of potassa, admitted. The globe before and after the 

 experiment was brought to the same temperature as the water 

 over winch the oxygen gas had remained. And Jis during the 

 short time required for the combustion there was no sensible 

 change either in the thermometer or barometer, no corrections 

 for pressureor temperature were rendered necessary ; the change 

 of volume in the gas after the combustion, was cstimaterl by 

 means of a fine tube connected with a stop-cock, adajited bv a 

 proper screw to the stop-cock of the globe, and the absorption 

 was judged of by the (quantity of mercury that entered the tube, 

 which afforfled a measure so exact that no alteration, however 

 mimite, could be overlooked. As the elastic force of the vapour of 

 water IS the same at the same temperature, it was evident, that if 

 any water formed in these experiments, it would be deposited as 

 dew or nust in the globe; ami I am convinced by direct trials, 



that 



