1869.] 



Mr. G. Gore on Hydrofluoric Acid. 



259 



All sulphides, except those of the alkaline-earth and alkali metals, exhi- 

 bited no change ; the latter evolved sulphuretted hydrogen violently. 

 Bisulphite of sodium dissolved with effervescence. Sulphates were variously 

 affected. The acid chromates of the alkali metals dissolved with violent 

 action to blood- red liquids, with evolution of vapour of fluoride of chro- 

 mium. Cyanide of potassium was violently decomposed, and hydrocyanic 

 acid set free. Numerous organic bodies (specified) were also immersed in 

 the acid; most of the solid ones were quickiy disintegrated. The acid 

 mixed with pyroxylic spirit, ether, and alcohol, but not with benzole ; with 

 spirit of turpentine it exploded, and produced a blood-red liquid. Gutta 

 percha, india-rubber, and nearly all the gums and resins were rapidly 

 disintegrated and generally dissolved to red liquids. Spermaceti, stearic 

 acid, and myrtle wax were but little affected, and paraffin not at all. 

 Sponge was also but little changed. Gun-cotton, silk, paper, cotton- wool, 

 calico, gelatine, and parchment were instantly converted into glutinous 

 substances, and generally dissolved. The solution of gun-cotton yielded 

 an inflammable film on evaporation to dryness. Pinewood instantly 

 blackened. 



From the various physical and chemical properties of the anhydrous acid, 

 the author concludes that it lies between hydrochloric acid and water, but 

 is much more closely allied to the former than to the latter. It is more 

 readily liquefied than hydrochloric acid, but less readily than steam ; like 

 hydrochloric acid it decomposes all carbonates ; like water it unites power- 

 fully with sulphuric and phosphoric anhydrides, with great evolution of 

 heat. The fluorides of the alkali metals unite violently with hydrofluoric 

 acid, as the oxides of those metals unite with water ; the hydrated 

 fluorides of the alkali metals also, like the hydrated fixed alkalies, have a 

 strongly alkaline reaction, and are capable of expelling ammonia from its 

 salts. It may be further remarked that the atomic number of fluorine lies 

 between that of oxygen and chlorine ; and the atomic number of oxygen, 

 added to that of fluorine, nearly equals that of chlorine. 



B. Aqueous Hydrofluoric Acid. 

 Under the head of the aqueous acid the author enumerates the various 

 impurities usually contained in the commercial acid, and describes the 

 modes he employed to detect and estimate them, and to estimate the 

 amount of H F in it. The process employed by him for obtaining the 

 aqueous acid in a very high degree of purity from the commercial liquid, 

 is also fully described. It consists essentially in passing an excess of sul- 

 phuretted hydrogen through the acid, then neutralizing the sulphuric and 

 hydrofluosilicic acids present by carbonate of potassium, decanting the 

 liquid after subsidence of the precipitate, removing the excess of sul- 

 phuretted hydrogen by carbonate of silver, distilling the filtered liquid 

 in a leaden retort with a condensing-tube of platinum, and, finally, 

 rectifying. 



