ON PYROXYLIC SPIRIT. &c. 117 



bestus ; and that chlorine or iodine only appeared after a considerable time in the 

 positive water, when acid had passed over into it, so as to afford room for a secon- 

 dary action.* These experiments were made with such moderate voltaic powers, 

 as 50 pairs of 2 inch plates, but still sufficiently energetic to decompose distilled 

 water, and, therefore, far more capable of producing the ordinary appearances in 

 solutions, of hydracids and haloid salts, when both poles were placed in the solu- 

 tion : and I have since had occasion fully to confirm the results, with stronger 

 powers. The consequence of employing more powerful batteries is just what might 

 have been anticipated. The chlorine, and particularly the iodine, make their ap- 

 pearance sooner, and why ? because acid is sooner carried over into the positively 

 electrified distilled water, as shown by test-paper, and because the reducing energy 

 of the battery from evolved oxygen is increased. 



Thus, when muriatic acid diluted with between twice and thrice its bulk of 

 water was placed in a tube A, Fig. 1, Plate II, of the capacity of 1^ dram, connect- 

 ed with the negative side of a battery of 72 pairs of 4 inch plates, and distilled wa- 

 ter in a similar tube B, connected with the positive side, the tubes being connected 

 with one another by a bundle of asbestus about ^th inch thick, acid was detected at 

 the positive pole within three or four minutes, with effervescence from both poles, 

 and in six minutes a very doubtful trace of the smell of chlorine was discernible, 

 but when test-paper was dipped into the liquids, no trace of bleaching was ob- 

 served. After half an hour's action, the smell of chlorine in B was still slight, and 

 the liquid in it showed an acid reaction, but no bleaching ; whilst the liquid of the 

 other tube neither had any smell of chlorine, nor did it bleach. The battery was 

 now reversed without replenishing it ; the platinum foil, which was in the water, 

 and had formerly been positive, being now connected with the negative side of 

 the battery, and the foil in the muriatic acid being now made the positive pole. 

 An instant pungent smell of chlorine arose from the now positive tube, with brisk 

 effervescence from the negative pole, and rather less from the positive ; and test- 

 paper was bleached at the positive pole as soon as the reaction was tried, which 

 was in less than one minute. 



When a moderately strong solution of hydriodic acid was next substituted 

 for the muriatic acid, all other circumstances being exactly the same as in the 

 commencement of the preceding experiment, and the voltaic power being the 

 same and in fresh action, a commencement of browning, as from the formation of 

 iodine, was observed, in about five minutes, in the liquid B, with effervescence 

 from both poles, and at the same time a slight acid reaction was observed on the 

 asbestus close to the same place. This browning went on increasing, and the 

 acid reaction became quite obvious at the positive pole, the effervescence still con- 

 tinuing there, although considerably less than at the negative pole. In about 



* Edinr. Trans, xiii., 339, et seq. 



