W. Skey. — On the Analogy of Cyanogen to Oxygen. 381 



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 0, while that of chlorine is Cl^ 0^, of bromine Br2 

 0^, etc j further Cy (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 + CU, 

 while that of the platino-cyanide is K^ + Pt^ + Cy^^, 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 



