On Chemical Equivalents. 105 



to be sphciical (which is the most simple hypothesis) ; la this 

 case, when different sorts combine singly, there is but one mode 

 of union. If they unite in the proportion of two to one, the two 

 particles will naturally arrange themselves at opposite poles of 

 that to which they unite. If they be three, they might be ar- 

 ranged with regularity at the angles of an equilateral triangle, 

 in a great circle surrounding the single spherule; but in this 

 arrangement, for want of similar matter at the poles of this cir- 

 cle, the equilibrium would be unstable, and would be liable to be 

 deranged by the slightest force of adjacent combinations : but, 

 when the number of one set of particles exceeds in the propor- 

 tion of 4 to 1, then, on the contrary, a stable equilibrium may 

 again take place, if the four particles are situated at the angles 

 of the four equilateral triangles composing a regular tetrahedron, 



'* But as this geometrical arrangement of the primary elements 

 of matter is altogether conjectural, and must rely for its confir- 

 mation or rejection upon future inquiry, I am desirous that it 

 should not be confounded with the results of the facts and observa- 

 tions related above, which are sufficiently distinct and satisfac- 

 tory with respect to the existence of the law of simple multiples. 

 It is perhaps too much to hope, that the geometrical arrangement 

 of primary particles will ever be perfectly known ; since, even 

 admitting that a very small number of these atoms combining to- 

 gether, would have a tendency to arrange themselves in the man- 

 ner I have imagined ; yet until it is ascertained how small a pro- 

 portion the primary particles themselves bear to the interval 

 between them, it may be supposed that surrounding combinations, 

 although themselves analogous, might disturb this arrangement; 

 and in that case, the effect of such interference must also be 

 taken into the account, before any theory of chemical combina- 

 tion can be rendered complete." , 



I am not aware, that any chemist has adduced experimental 

 evidence, to prove that a " stable equilibrium may again take 

 place, if the four particles are situated at the angles of the four 

 equilateral triangles composing a regular tetrahedron." I have, 

 therefore, much pleasure in referring to my researches on the 

 constitution of liquid nitric acid, as unfolding a striking confir- 

 mation of Dr. Wollaston's true philosophy of atomical combina- 

 tion. When I wrote the following sentence, I had no recollec- 

 tion whatever of Dr. Wollaston's profound speculations on tctra- 

 hedral arrangement. — " We perceive, tiuit tiie liquid acid of 

 1"420, composed of 4 primes of water + 1 of dry acid, pos- 

 sesses the greatest power of resisting the inlluence of tem|)erature 

 to change its state. It retpiires the vuiximum heat to boil it, 

 when it distills unchanged ; and the maximum cold to effect its 

 congelation." See Acid (Nitric), in this Dictionary. 



Vol. 57. No. 274. FeO. 1821. O Hero 



