in Chemical Comhinalions, 347 



of salt is formed by the junction of one octohedron of oxygen, 

 two tetrahedrons of nitrous gas, and four tetrahedrons similar 

 to those which enter, to the number of two, into each particle 

 of ammoniacal gas : the representative form of this particle is 

 therefore a pyramidated hexa-tetrahedron, containing ten mole- 

 cules of oxygen, eight of azote, and twelve of hydrogen. When 

 we decompose the salt by heat, the eight molecules of azote 

 form two particles of oxide of azote with four molecules of oxv- 

 gen, and the twelve molecules of hydrogen form three parti- 

 cles of water with the six other molecules of oxvgen. 



When the salt contains besides water of crystallization, we 

 ought to obtain more than tiiree particles of water; but in all 

 cases, we can only extract from its decomposition water and 

 oxide of azote, as we find by experience. 



If the quantity of water of crystallization vvas equal in the 

 salt to that which is contained in the most highly concentrated 

 nitric acid, it would be necessary to join to the octohedron and 

 to the six tetrahedrons of which one of the particles is composed, 

 two other octohedrons of water ; wliich will give for tlie r^^-pre- 

 sentative form of the crystallized nitrate of ammonia, an octo- 

 ccntahedroa formed by the meetmg of six tetrahedrons and 

 one trioctohedron. Chlore is combined with hydrogen in equal 

 volume, and the muriatic ac'd gas which results occupies a vo- 

 lume equal to the sum of the volumes or those two component 

 parts. We might account for this mode of combination," by 

 supposing that the representative forms of the particles of chloie 

 are isolated tetrahedrons like those of oxygen, azote, and hy- 

 drogen ; that of the particles of the muriatic acid will tlien be 

 a tetrahedron : but we may also explain it by considering each 

 ])article of chlore as formed by the meeting of two tetraliedrons 

 in a parallelopipedon, and as conseijuently containing eiglit mo- 

 lecides. This last hypothesis is the only one which can agree 

 with the proportions of the other combinations of chloie, the 

 phaiiiomena which they exhibit, and the properties which dia- 

 lacterize them. 



By admitting it, we find that each particle of muriatic acid, 

 containing the half of a particle of hydrogen and the half of 

 a particle of chlore, has for its representative form an octohe- 

 dron composed of two molecules of hydrogen and four molecules 

 of chlore. When the muriatic gas is combined with the am- 

 moniacal gas, each of its octohedrons is combined with a cubic 

 particle of this gas : hence it follows, that it ought to absorb 

 of it a volume equal to its own, as experience shows, and that 

 the particles of the salt thus formed ought to have as their re- 

 presentative form a rhomboidal dodecahedron : this form is, in 

 factj one of those which belong to the system of crystallization 



of 



