ME. G. GOEE ON HYDEOELU OEIC ACID. 
189 
for opportunities, it was found that the passage of the current was not attended by any 
distinct increase of gas from the anode. No special odour could be detected above the 
anodes, but on removing the charcoal from the liquid it evolved a feeble odour some- 
what like that of chlorine, in addition to the intense one of the acid. The kinds of 
wood employed for making the charcoal were beech, kingwood, ebony, lignum-vitae, 
box, mahogany, zebra, Memel oak, English oak, rosewood, maple, lancewood, walnut, 
Norwegian pine, and iron wood. The fracture of the carbons was not caused by the low- 
ness of the temperature of the acid. 
With an anode of pure sheet gold the acid scarcely conducted at all, except for a short 
time, even with forty Smee’s elements ; by continuing the action about 1|- hour, the 
anode acquired a dark reddish-brown film and a few crystals upon its edges, which were 
at first of a green colour, but became red by exposure to the air. With a palladium 
anode the acid conducted somewhat less freely than with one of platinum or gas-carbon ; 
and by employing forty Smee’s elements the palladium anode was also corroded. The 
salts which fall off the anodes appear to be wholly converted into metal by the dissemi- 
nated minute bubbles of hydrogen, and even some of the coating of the anode itself is 
partly so converted if the hydrogen is allowed to come into contact with it. The action 
in the electrolysis-cell was sometimes watched by the aid of a magnesium light, as the 
fume was usually too dense to admit of inspection by ordinary light. 
The most effective form of electrolytic apparatus employed is represented by the 
annexed figure. A A is a circular and deep platinum cup ; B B 
is a shallow and loosely fitting cup of paraffin provided with a 
handle (not shown) ; C C is a wide tube of platinum open at both 
ends, and fixed at its upper end within an equally wide circular 
perforation in the annular paraffin stopper, DD; E E is an inner 
stopper of paraffin fitting within the other, and supporting a sheet 
of platinum or other metal, F F, which passes through it and con- 
stitutes the anode. The use of the tube C C is to prevent the 
hydrogen evolved at the inner surface of the cathode, A A, coming 
into contact with the anode, F. The tube C C is coated on its 
outer side at its lower end and up to a short distance above the 
level of the liquid with a thin layer of paraffin, to prevent the ten- 
dency of electrolytic action upon the tube C C. Electrolysis tends 
to first decompose any traces of water the acid may contain, and 
thus maintain the acid in an anhydrous state. 
Two ounces of strong sulphuric acid was added to a mixture of 336 grains of pure 
fluoride of sodium and 472'5 grains of nitrate of potassium, both in fine powder, in a 
platinum retort, the mixture distilled, and the product received in a platinum bottle. 
The distillate weighed 678-2 grains, it should have weighed only 664 grains; the excess 
was probably water, from the sulphuric acid not being of maximum strength. In apply- 
ing the heat, the retort was immersed in a bath of linseed-oil, the temperature of which 
MDCCCLXIX. 2 D 
Fig. 13. 
