Page:Transactions NZ Institute Volume 7.djvu/463

Rh detach from the negative pole; while in reference to the similarity in the crystalline forms of cyanide of potassium to the chloride, so many substances crystallize in the same form, though these are of a widely different nature, that, as a single test of position, form can be of little value.

Thus I think the grounds upon which we class cyanogen in this manner do not when carefully examined prove at all sound, but it rather appears, if admission to the group of halogens is given to cyanogen, that we must upon principle further admit within it substances, such as sulphur and oxygen, which obviously should not enter there.

But, outside anything yet stated, it is indisputable that the heavy metallic cyanides do not correspond in general with the chlorides, bromides, etc., of this series of metals; except in the case of the silver salts, there is no appearance even of harmony in this direction.

Again, the most stable oxygen compound of cyanogen is, according to the new chemical notation, Cy O, while that of chlorine is Cl$2$ O$5$, of bromine Br$2$ O$5$, etc; further Cy O (cyanic acid) forms compounds with the metals which are generally insoluble in water, alcohol, or ether; while chloric acid, its alleged analogue, generally forms compounds with them, possessing considerable solubility in these liquids. There is in fact as great a difference between the two acids and their metallic compounds on these points as there is between carbonic and nitric acid and between their respective metallic compounds; further, the composition of platino-chloride of potassium is K + Pt + Cl$4$, while that of the platino-cyanide is K$4$ + Pt$2$ + Cy$10$, exhibiting again a marked difference.

The great dissimilarity existing between cyanogen and the elements of the chlorine group, analogically considered, being thus shown, and the ground I hope consequently ready for the reception of a better classification than the one attacked, I now proceed to show what I conceive to be the proper position of cyanogen in regard to the elements. For this purpose I will refer you to the supposed points of resemblance between this substance and chlorine, which I have just criticised, and I think you will find that, wherever the true character of cyanogen is correctly stated, it agrees precisely with that of oxygen.

Thus, to recapitulate a little, oxygen, especially when in the allotropic form, combines directly with metals generally, including gold and silver, moreover it combines with hydrogen to form a neutral compound, and this when electrolyzed delivers its oxygen at the positive pole. Besides this cyanogen resembles oxygen, wherein, as shown, it differs from the chlorine group, its compound with the alkaline metals being caustic, and those with the heavy metals characterized by great insolubility in water, while several of these cyanides are soluble in alkaline cyanides, precisely as several of the