712 PHILOSOPHICAL TRANSACTIONS. [aNNO \7Q0. 



substances, and particularly in recent healthy pus ; Dr. C. took equal quantities 

 of the latter, and of ash-coloured cancerous matter, and having diffused each of 

 them through thrice its weight of distilled water, he added to them equal quanti- 

 ties of concentrated vitriolic acid ; the weight of the acid being nearly the same 

 with that of the matter used in the experiment. The mixture containing the pus 

 acquired from the acid a faint brown colour ; but that which contained the can- 

 cerous matter, was suddenly changed to a deep brown, approaching to black. 

 When these mixtures were diluted. with about twice their weight of distilled water, 

 the brown tinge of the former entirely disappeared ; but the latter still retained 

 its brown colour, though it was somewhat fainter than it had been on the first 

 addition of the acid. 



The aerial fluid which was disengaged in the foregoing trials from the matter 

 of cancer, by the vitriolic acid, appeared from its odour to have a nearer resem- 

 blance to hepatic than to any other species of air. As it seemed, from its sensible 

 qualities, to be a very active, and probably a deleterious principle, he endeavoured 

 more particularly to inquire into its nature, and to compare it with common 

 hepatic air. But before relating the trials which were made with that view, it 

 may not be improper briefly to mention the characters by which common hepatic 

 air is distinguished. It has a smell resembling that of rotten eggs ; it is inflam- 

 mable, and during its combustion in the open air, sulphur is deposited ; it com- 

 municates a black colour to silver and copper, and a brownish tinge to lead and 

 iron ; it is soluble in water, and when a solution of nitrated silver is dropped into 

 water impregnated with it, the mixture becomes turbid, and a dark-coloured pre- 

 cipitate falls to the bottom ; by the addition of the nitrated silver, the odour of 

 the hepatic air is rendered much fainter ; and it is entirely destroyed by concen- 

 trated nitrous, or by dephlogisticated marine acid. 



To determine whether the aerial fluid contained in the cancerous matter pos- 

 sessed these properties, a portion of this substance was diffused through distilled 

 water. The mixture being filtered, a small quantity of nitrated silver was dropped 

 into it. In a little time, an ash-coloured cloud was produced, which soon after- 

 wards acquired a brownish purple hue, and at the end of 2 hours the colour of 

 the mixture was changed to a deep brown. The fetid smell was now rendered 

 much fainter than that of a similar mixture of cancerous matter, and of distilled 

 water, to which nitrated silver had not been added. When a little concentrated 

 nitrous acid was dropped into the mixture which had been thus altered by the ad- 

 dition of nitrated silver, a slight effervescence took place, the brown hue was in- 

 stantly changed to an orange colour, and the fetid smell was abolished. The 

 fetor was likewise entirely destroyed, when dephlogisticated marine acid was added 

 either to cancerous matter in its separate state, or to a portion of that substance 

 which had been previously mixed with nitrated silver. 



