Mr. Faraday on the Limits of Vaporisation. 75 



No. 9. Bottle, a little solution of persulphate of iron ; tube, 

 crystals of the ferro-prussiate of potash. Both were un- 

 changed ; there was no appearance of Prussian blue about 

 either the crystals or solution ; neither of the salts had been 

 volatilised. 



No. 10. Bottle, a little solution of potash ; tube, fragments 

 of calomel. Here the potash had acted upon the glass, as in 

 No. 6; but, with respect to the calomel, the volatility of which 

 was in question, there was not the slightest trace of such an 

 effect. No black oxide nor other substance existed in the 

 potash solution which could allow the presumption that any 

 calomel had passed. 



No. 11. Bottle, solution of potash; tube, fragments of cor- 

 rosive sublimate. Here the potash had acted on the glass as 

 before ; carbonic acid had also gained access by the stopper ; 

 so that no caustic potash was present ; but there were distinct 

 appearances of the sublimation of corrosive sublimate, and 

 minute crystals of the substance were even attached to the 

 under part of the stopper in the bottle. Hence corrosive 

 sublimate is volatile at common temperatures. 



No. 12 and 13. Bottles, solution of chromate of potassa; 

 tubes, in one, chloride of lead in powder, in the other nitrate of 

 lead in crystals. In both these experiments the chromate of 

 potash had acted upon the lead of the glass, and rendered it 

 yellow and dim ; so that no indication could be gathered 

 relating to the non-volatility of the compounds of lead. 



No. 14. Bottle, solution of iodide of potassa ; tube, chloride 

 of lead. Both remained unaltered; the solution of iodide was 

 perfectly clear and colourless ; no trace of the chloride of lead 

 had passed over in vapour. 



No. 15. Bottle, solution of muriate of lime; tube crystals of 

 carbonate of soda. A part of the water has passed to the car- 

 bonate of soda; but both it and the remaining solution of 

 muriate of lime are perfectly clear. No portion of either salt 

 has volatilised from one place to another. 



No. 16. Bottle, dilute sulphuric acid ; tube, nitrate of am- 

 monia in fragments. The nitrate was slightly moist. The 

 acid being examined was found to contain nitric acid, whilst 

 the test acid, No. 7, was perfectly free from it. It would 



