74 Mr. Faraday on the Limits of Vaporisation. 



lower surfaces, but that no vapour has risen to the upper part 

 of the tube. On examining the solution by a drop or two of 

 pure ammonia, it was however found that a slight precipitate 

 of oxalate of ammonia occurred. The experiment shews, 

 therefore, that oxalic acid is volatile at common temperatures, 

 and had not only formed crystals in the tube, but has passed 

 over to the solution of lime. 



No. 4. Bottle, solution half sulphuric acid, half water; tube, 

 crystallized common salt. No water has passed to the salt. 

 On opening the bottle, the clear diluted sulphuric acid was 

 examined for muriatic acid, but no trace could be found. 

 Hence chloride of sodium has not been volatilised under these 

 circumstances. 



No. 5. Bottle, solution of muriate of lime ; tube, crystals of 

 oxalate of ammonia. The oxalate of ammonia appeared quite 

 unchanged. The solution of muriate of lime was perfectly 

 clear ; but when a little pure ammonia was added to it, a very 

 faint precipitate of oxalate of lime was produced. 



No. 6. Bottle, little solution of potash ; tube, white arsenic 

 in pieces and powder. This bottle was opened because of the 

 appearances, in October, 1829, and had then remained three 

 years undisturbed. The arsenious acid was to all appearance 

 unchanged. The solution of potash was turbid and foul. On 

 chemical examination, it proved to have acted powerfully on 

 the glass. It had dissolved so much silica as to become a soft 

 solid, by the action of an acid, and it had also dissolved a con- 

 siderable quantity of lead ; but there was no trace of arsenious 

 acid in it; so that this substance, although abundantly volatile 

 at 600, had not risen in vapour when aqueous vapour and air 

 was present at common temperatures. 



No. 7. Was some of the sulphuric acid used in these expe- 

 riments, preserved for comparison. 



No. 8. Bottle, solution half sulphuric acid, half water ; tube, 

 pieces of muriate of ammonia. When this bottle was opened, 

 the pieces of muriate of ammonia presented no appearance of 

 change ; there was no moisture about them, nor any ap- 

 pearances of dissection that I could distinguish. The diluted 

 sulphuric acid being examined by sulphate of silver, gave no 

 appearances of muriatic acid; so that muriate of ammonia 

 appears fixed under these circumstances. 



