502 Mr. J. Denham Smith on the 



thus laid down I have followed; and have tortured it in every 

 way, using hot and cold, weak and strong, solutions — adding 

 potash till the solution was perfectly neutral, and also until it 

 became distinctly alkaline, but all to no purpose ; I could in 

 no way, nor in a single instance, obtain a salt containing less 

 sulphuric acid than the pentasulphate^ SO a 5CuO, 6 HO. 

 When an excess of alkali was added, the precipitate would 

 often change to a greenish-brown tint, but all my efforts to 

 obtain the green salt described by Dr. Kane were fruitless. 

 The composition assigned to this salt, S0 3 8CuO, 12HO, is 

 a most singular and extraordinary one, and on account of this 

 singularity it deserves considerable attention; if a portion of 

 this salt be sent to me I will submit it to analysis, and should 

 it really be found to exist, shall be happy to bear witness to 

 that effect ; but at present must confess that I do not believe 

 in its existence. I perhaps may be pardoned the suggestion, 

 but it is not impossible, if the solution of potash was not quite 

 free from carbonic acid, that a mixture of subsulphate, hydrate, 

 and carbonate of copper might be obtained, which on analy- 

 sis, reckoning the carbonic acid expelled by the second heat- 

 ing with spirit lamp as water, would afford results closely 

 approximating to such a constitution as S0 3 8CuO, 12HO. 



On a review of these subsulphates, the question respecting 

 the function of the water contained in them naturally presents 

 itself, and it is one well worthy consideration on account of 

 the highly distinguished authorities who have advocated par- 

 ticular theories on this subject, which at present are usually 

 admitted, or at least are not disputed. 



Professor Graham, in the paper " On the Constitution of 

 the Oxalates," &c. &c, seems to decline the question, for 

 speaking of the subsulphates of copper and zinc, he says, 

 " When most successfully prepared they were found to con- 

 tain four atoms of metallic oxide to one of acid (instead of 

 three atoms of oxide, as M. Berzelius supposed)." Berzelius 

 supposed rightly, there is a trisulphate, " together with four 

 atoms of water. I have not hitherto been able to form a di- 

 stinct idea of their constitution, or to decide between differ- 

 ent views which may be taken of it ;" yet in the previous page 

 Mr. Graham writes, " In a former paper upon water as a 

 constituent of sulphates, I examined particularly the constitu- 

 tion of hyd rated sulphuric acid and of the sulphates of the 

 magnesian class of oxides" (copper is included in this class). 

 " All these salts contain one atom of constitutional water;" 

 and again, " all salts are neutral in composition." Now it 

 appears to me that if these two laws be true, that not only 

 should all these subsulphates of copper lose all their com- 



