174 DR SAMUEL BROWN ON PARACYANOGEN. 



two elements of action, high temperature and great pressure ; the former be- 

 ing the sole principle of experiment 1, the latter of experiment 8, and both 

 being concerned in the other seven. It is impossible to change a whole equi- 

 valent of cyanogen by this kind of procedure, for no apparatus can be so filled 

 with salt as to leave no space for extricated gas, and, as has been several times 

 observed already, paracyanogen absorbs it largely. Whatever may be the value 

 of the foregoing results as the first-fruits of a new field of chemical investigation, 

 viz. the decomposition of compound bodies under greater than atmospheric pres- 

 sure, and at temperatures higher than their natural points of reduction, they at 

 least supply the desideratum of a simple process for the large preparation of a 

 curious substance, which eminently deserves to be studied, but has hitherto been 

 procured only in small residual quantities. Process. Let any quantity of cyanu- 

 ret be tightly packed into a tube of cast copper, eight inches long and two-thirds 

 of an inch in diameter, shut at one end and open at the other ; let the mouth be 

 plugged an inch down with stucco-paste, and a little fire-clay put over the stucco ; 

 and, after the tube has been luted and dried, let it be kept half an hour at an 

 obscure red heat. The greater part of the nitro-carbon product remains in the 

 form of paracyanogen. If it contain unreduced cyanuret it must be returned, if 

 it contain mercury it may be cleaned in a leaden mortar, and it may be rendered 

 perfectly pure by solution in concentrated sulphiiric acid. By this and similar 

 processes I have made paracyanogen by the drachm instead of the grain, having 

 always procured about two-thirds of the Avhole weight of nitrogen and carbon. 

 The mercury may be collected by adapting a conducting tube and receiver to the 

 copper-tube and plug. This process may be variously modified. I employ two 

 copper-tubes, one of which terminates at its open end in a male screw, and the 

 other in a female. The latter, thrice as long as the former, is charged, and the 

 two are firmly screwed together so as to give very great, but not fixed, pressure, 

 for the screws always permit gaseous passage in such circumstances. 



V. The Constitution of Paracyanogen. It is isomeric with cyanogen. Ana- 

 lysis thus suggests two possible arrangements of its components : It may be re- 

 garded as a compound of two combined atoms of nitrogen and four combined 

 atoms of carbon, and represented by the symbol N 2 + 4 ; or, it may be viewed as 

 a combination of two atoms of cyanogen, with the symbol Cy + Cy, or Cy 2 . These 

 are the only schemes of constitution which can be formed, without supposing radi- 

 cals which are not known to exist, and modes of combination of which there is no 

 known example. Both of them assume the combination of " equal and similar" * 



, * I have borrowed the phrase " equal and similar" from geometry, because several atoms are equal 

 which are not similar. It implies identity both of atomic weight and of true isomorphism, both of force 

 and of form. 



