388 Transactions. — Chemistry. 



instead of being yellowish green, as our present knowledge upon the matter 

 would lead us to expect. 



7. That if the ammoniacal solution prepared as above is acidified before 

 the application of the ferro-cyanide thereto, the precipitate which then 

 ensues is of the colour we should look for that is yellowish-green. 



8. That as far as I have yet examined this dark precipitate, it appears 

 to be the ferri- cyanide of cobalt. 



It thus appears that both zinc and cobalt oxides may, when in contact 

 with certain salts, give us reactions which are altogether different to those 

 which we have hitherto been cognizant of; consequently these oxides are 

 capable of, and actually do in these cases, assume an allotropic form. 



The characteristic of these oxides when in this form, is that they change 

 the quantivalence or degree of basicity of ferro- and ferri-cyanic acids, so 

 that they are transformed the one iuto the other (the acids themselves 

 being, as you may remember, isomeric). Thus accomplishing that for which 

 an oxidation or de-oxidation process has hitherto been deemed necessary. 



I should in this connection inform you that manganese oxide, in solu- 

 tion, when boiled with ammonia in excess refuse to afford a precipitate 

 with potassic ferri-cyanide. We only get this by acidifying the solution. 



It seems therefore that careful cognizance should be taken of these facts 

 by anyone making a quahtative analysis for the metals referred to, and 

 using for this either of the tests above-named. The urgent necessity there 

 may be for " acidifying " and then "boiling " the solution in the one case and 

 of acidifying in the other, is clearly shown. If these precautionary opera- 

 tions are not taken zinc may be mistaken for lead, and cobalt for copper. 



Art. LIII — On a Periodide and an lodo-Carbonate of Lead. 

 By William Skey, Analyst to the Geological Survey Department. 

 [Read before the Wellington Philosophical Society, Ath December, 1880.] 

 If to a solution of a lead- salt and borax iodine dissolved in an aqeous 

 solution of potassic-iodide is added a crystaline precipitate copiously forms, 

 and which differs from the only plumbic -iodide which we now know in being 

 of a brick-red colour (instead of yellow), and in being far less soluble in 

 water than it. 



I have not had time to fully analyse this new compound, but it is 

 undoubtedly the per-iodide of lead. I merely note it here and the manner 

 of its production, as it forms the basis of the salt which I desu-e espe- 

 cially to bring before your notice. 



