﻿Mr. G. Gore on Hydrofluoric Acid. 473 



fected; but those of the alkaline- earth and alkali metals were strongly 

 decomposed, and iodine (in some cases only) set free. The anhydrous 

 acid decomposed all carbonates with effervescence, and those of the 

 alkaline-earth and alkali metals with violent action. Borates of the 

 alkalies also produced very strong action. Silico-fluorides of the 

 alkali metals dissolved with effervescence. All sulphides, except 

 those of the alkaline-earth and alkali metals, exhibited no change ; 

 the latter evolved sulphuretted hydrogen violently. Bisulphite of so- 

 dium 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 hydro- 

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

 immersed in the acid ; most of the solid ones were quickly disin- 

 tegrated. 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 ge- 

 nerally 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 powerfully with sulphuric and phosphoric anhy- 

 drides, 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 reac- 

 tion, 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 HF 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 es- 

 sentially in passing an excess of sulphuretted hydrogen through the 

 acid, then neutralizing the sulphuric and hydrofluosilicic acids pre- 

 sent by carbonate of potassium, decanting the liquid after subsidence 



