ME. G. GOEE ON HYDEOFLUOEIC ACID. 
199 
dilute pure hydrofluoric acid of about 10 per cent, by means of six Smee’s cells, a platinum- 
foil anode, and a platinum crucible cathode. Gas was liberated freely from each electrode, 
and a very strong odour like that of ozone was evolved. No corrosion of either electrode 
took place during twelve hours’ action. I also electrolyzed the same acid by six Grove’s 
cells and platinum electrodes, the anode being enclosed air-tight within a gutta-percha 
funnel inverted in the acid, an exit-tube with a tap being in the side of the neck of the 
funnel for regulating the escape of the gas. Free conduction occurred. Plenty of gas 
was evolved. The gas from the anode smelt powerfully of ozone, and inflamed a red-hot 
charcoal splint vividly. Paper wet with spirits of turpentine was not blackened in the 
strongly issuing stream of gas, nor was bright silver affected in it. No corrosive action 
occurred upon the anode. I prepared some pure hydrofluoric acid containing about 80 
per cent, of anhydrous acid, by taking one part by weight of 40 per cent, pure hydro- 
fluoric acid in a bent tube C (of the apparatus, page 197) immersed in a stream of cold 
water, and passing through it about two parts by weight of anhydrous hydrofluoric acid 
vapour, obtained by very gradually fusing and heating to redness eight parts of anhydrous 
double fluoride of hydrogen and potassium contained in the platinum tube-retort A, to 
which the bent platinum tube was fixed. The acid thus obtained was electrolyzed by 
ten Smee’s cells with platinum electrodes in a narrow and deep platinum cup, the cup 
being the negative pole. Copious conduction occurred ; a powerful odour of ozone was 
evolved, indicating decomposition of the water and evolution of oxygen gas at the anode ; 
much gas was liberated, and doubtless consisted chiefly of hydrogen. Heat was evolved 
in the liquid by the conduction-resistance. The anode dissolved, but not very rapidly ; 
in three hours it lost T58 grain, and indicated the simultaneous decomposition of the 
acid with that of the water, the latter being the greatest in amount. The smell of ozone 
disappeared if the battery was weak, and reappeared on first contact. In a further 
eleven hours the anode lost 5‘05 grains, and was covered with a blackish crust; this 
crust was partly soluble in water to a brownish solution. In a further twenty-two hours 
the loss had increased from 5‘05 to 15'00 grains without any signs of an electro-deposit 
of platinum upon the platinum cathode tube. The total loss of the anode was 
l'58+15'OO grains=16‘58 grains. Found 15-5 grains of black-brown powder which 
showed some metal by pressure between surfaces of agate. I also electrolyzed pure 30 
per cent, hydrofluoric acid by platinum electrodes and ten Smee’s cells, the liquid being 
mixed with other pure acids. With equal volumes of hydrofluoric acid and concentrated 
nitric acid, gas was evolved freely from the anode ; it had no odour of ozone, and was 
probably ordinary oxygen. No gas was visible at the cathode; the liberated hydrogen 
was doubtless absorbed by the nitric acid. Only a trace of platinum was dissolved during 
sixteen hours’ action ; the liquid was then pale yellow, but became dark green, evolved 
abundance of red-brown fumes, and became hot on addition of water. With equal 
volumes of aqueous hydrofluoric and strong hydrochloric acids, much chlorine was 
evolved from the anode and hydrogen from the cathode ; this agrees with the usual 
results, that chlorides (as well as oxides) are decomposed before fluorides, and hydro- 
