On the Action of Medicines, &c. 337 



probable, according to the experiments of Gay Lussac, and also 

 tliose which I have made known, that the crystalline substance 

 described by Messrs. Clement and Desormes, in the memoir in 

 which they have explained the formation of the sulphuric acid, 

 is nothing but this combination. 



Since the above memoir was publicly read, 1 have observed 

 that the nitrous acid may be presented under very different co- 

 lours, according to the temperature to which it is subjected. 

 The orange-yeliow colour which I bave assigned to it in the 

 course of this paper, is that which it has at the temperature 

 from 15 to 28: it is deeper the more it approaches its point of 

 ebullition. At this temperature it is almost red ; and we know 

 that at an elevated temperature its vapour is of a very deep red. 

 But below 15^ the colour becomes weaker and weaker, down to 

 0% then it is no longer of a fawn jellow; at —10^ it is nearly 

 colourless ; and finally, at —20° it is entirely so. We may 

 easily produce those different shades by shutting up in the bulb 

 of a thermometer a certain quantity of dry nitrous acid, the 

 temperature of which is lowered successively by the evaporation 

 of ether, or carburet of sulphur. It will be curious to observe 

 if the same liquid subjected to a temperature of —40' or —.50" 

 will be presented again under a coloured form ; and if this co- 

 lour will be blue, as indicated by the theory of coloured rings: — 

 this I shall endeavour shortly to ascertain. 



LXVI. Experiments and Obiervations to prove that the lene- 

 ficial BJfccts of mumj Medicines are produced through the 

 Medinm of the circulating Blood, more particulurlij that of 

 the Cokhicum aulumnale iipon the Gout. By Sir Everard 

 Home, Bart. F.P.R.S. Communicated hy the Society for 

 improving Animal Chemistry*. 



A. KNOWJ.HDGE of the readiness with which liquids pass from 

 the stomach into tlie circulation, carrying along with them the 

 impregnation of different medicines ; and the readiness with 

 which such medicines are carried off from the circulating blood, 

 bv the action of the kidneys, led Mr. Brande and myself to an 

 inquiry respecting the prevention of gravel and gout, upon which 

 subject he has laid two separate papers before the Society. 



In these communications, the action of different substances 

 on the contents of the stomach has been considered, and those 



* From the 'IVansnctioiis of the Royal Society for 1816, part ii. 



Vol. 48. No. 223. iVo>'. 1816. Y substances 



