299 



and boiled. The acid is thus so perfectly purified from nitric acid, 

 that when used for making hydrochloric acid, it yields a product 

 quite colourless, which was not the case with the oil of vitriol puri- 

 fied by any other process. 



If the oil of vitriol be diluted with one-half its volume of sulphur- 

 ous acid solution (or of water, previously to passing the gas through 

 it), the sulphate of lead is also totally separated, and the clear liquid, 

 decanted from the precipitate, and boiled down to sp. gr. 1*845, is 

 colourless, and almost chemically pure. 



2. On the Preparation of Pure Hydrochloric Acid. 



Professor Gregory, in his process for preparing hydrochloric acid, 

 by heating 1 equivalent of sea-salt with 2 equivalents of sulphuric 

 acid of sp, gr. 1650, directs the use of patent salt, to avoid the pre- 

 sence of iron in the product. 



The author observed, that there is always a certain quantity of 

 iron in the residue, even when patent salt is used ; but that none 

 passes over with the hydrochloric acid. He then added iron and 

 peroxide of iron in considerable quantity to the materials. Still no 

 iron passed over. It would appear, that when iron had been ob- 

 served by Professor Gregory in minute quantity, in the hydrochloric 

 acid made by his process, from common salt, it had either passed 

 over at the very end of the process, when the temperature rose very 

 high, although the author could not, in his own experiments, ob- 

 serve this, or, more probably, had been present in the test employed. 

 It is probable that, even when much iron is present in the materials, 

 the presence of the excess of sulphuric acid, and also the low tem- 

 perature at which the process goes on, prevent the formation of the 

 chloride of iron. 



The author's observations enable us to prepare, from the com- 

 monest and cheapest salt, perfectly pure and colourless hydrochloric 

 acid, and thus still further to reduce the price of this reagent, so 

 essential to the chemist. 



Professor Gregory also briefly stated some observations by Mr 

 Kemp and himself, on the purification of chloroform, which he was 

 to describe more fully at a subsequent meeting. 



Dr Stark 



Was balloted for, and duly and unanimously re-elected a 

 Fellow of the Society. 



