Chemical Science, 167 



levity, to mingle with the gas appropriate to each particular 

 pole * ? 



We can by no means consider Professor Silliman's account as at all 

 altering the state of our knowledge relative to where the decompo- 

 sition of water occurs, between or at the voltaic poles. The Pro- 

 fessor seems to imply that it takes place at both poles, quoting the 

 two currents from each pole as the proof; but there is no proof that 

 the two currents were not of the same gas, i.e., both oxygen at the 

 positive and both hydrogen at the negative pole ; and, in fact, that 

 is the only way of accounting for the mixture of both gases in 

 both receiving tubes. There is great reason to believe that the 

 arrangement of the gas at each pole into two currents, one internal 

 and the other external to the receiving tube, was a mere conse- 

 quence of the descending water carrying off the smaller bubbles 

 with it. Ed. 



2. POWER OF METALLIC RODS, OR WIRES, TO DECOMPOSE 

 WATER, AFTER THEIR CONNEXION WITH THE GALVANIC 

 PILE is BROKEN. (Berzelius.) 



In the experiments which I undertook in 1806, 7, in company with 

 Mr. Hisinger, we had found that rods of metal which were em- 

 ployed to decompose water by means of the galvanic pile, continued 

 to develope gas after their connexion with the pile had ceased, a 

 circumstance which seemed to indicate a continuance of electrical 

 state, though these rods shewed no action upon any other portion 

 of liquid, even of the same kind, than that in which they had been 

 placed during their contact with the pile. This observation, which 

 I had almost forgotten, has been lately confirmed by Pfaff, who has 

 also added to it several others of a similar kind. We might suppose 

 such effects to be produced by a residual polarity, both in the liquid 

 and the metal, shewing itself, as long as it continues, by a continua- 

 tion of chemical action ; but some of Pfaff 's experiments seem to 

 oppose this idea, for he found that the addition of ammonia to the 

 liquid, by which all its internal polarity was destroyed, did not 

 deprive the wires of their effect. The metals which acquire this 

 property in the highest degree are iron and zinc, next to which 

 is gold. He attempts to explain the phenomenon, by supposing 

 that the continued passage of the electrical stream had brought the 

 elements of the water nearer to a state of separation, so that a very 

 slight influence was sufficient to destroy their union. It must be 

 confessed, however, that we cannot at present advance a satisfactory 

 explanation!. 



3. ON PYROPHOSPHORIC ACID AND THE PYROPHOSPHATES. 



Mr. Clarke first pointed out the singular change induced upon the 

 phosphates by calcination, and, conceiving the acid was changed 

 in its nature, gave it in its new condition the name of Pyrophos- 



* Silliman's Journ., xviii. 199. f Berzelius, Arsberattelse, 1829, p. 33. 



