Note 214 — RESEARCH IV.

In a conversation with Mr. Watt, relating to the powers of gases, that excellent philosopher told me he had for some time entertained a suspicion, that the effects attributed to oxygene produced from manganese by heat, in some measure depended upon nitrous acid suspended in the gas, formed during ignition by the union of some of the oxygene of the manganese with nitrogene likewise condensed in it.

In the course of experiments on nitrous acid, detailed in Research I. made in September, October, and December, 1799, I several times experienced a severe oppression on the chest and difficulty of respiration, not unanalogous to that produced by oxygene, but much more violent, from breathing an atmosphere loaded with nitrous acid vapour. This fact seemed to confirm Mr. Watt’s suspicion. I confess, however, that I have never been able to detect any smell of nitrous acid, either by means of my own organs or those of others, during the production of oxygene; when the gas is suffered to pass into the atmosphere. The oxygene breathed in the experiments detailed in the text, had been for some days in contact with water.