106 On Chemical Equivalents. 



Here we have a fine example of the stabihty of equilibrium, 

 introduced by the combination of four atoms with one. The 

 discovery which I had also the good fortune to make with regard 

 to the constitution of aqueous sulphuric acid, that the maximum 

 condensation occurred, when one atom of the real ticid was com- 

 bined with three atoms of water, is equally consonant to Dr. 

 Wollaston's views. "^ But in this arrangement," says Dr. Wol- 

 lastqii, " for want of similar matter at the poles of this circle, 

 the equilibrium would l)e unstable, and would be liable to be 

 deranged by the slightest force of adjacent combinations." Com- 

 pare with this remark, the following sentence irom my paper on 

 sulphuric acid, as publi^hed in the Journal of Science, October 

 ISI7. — " The terms of dilution are, like logarithms, a series of 

 numbers in arithmetical progression, corresponding to another 

 series, namely, the specific gravities, in geometrical progression. 

 iFor a little distance on both sides of the point of greatest con- 

 densation, the series converges with accelerated velocity, whence 

 the 10 or 12 terms on either hand, deviate a little from experi- 

 ment." Page 126. Or in other words, a small addition of water 

 or of acid to the above atomic group, produces a great change 

 on the degree of condensation ; which accords with the position 

 *' that the e(|uilibrium would be liable to be deranged by the 

 slightest force of adjacent combinations." 



While considering this part of Dr. Wollaston's important pa- 

 per, let me advert to the curious facts pointed out in the article 

 Nitric Acid, relative to the compound of one atom of dry acid 

 and seven atoms water. In my paper on the subject, published 

 in the eiy,hth number of the Journal of Science, I showed, that 

 this liquid combination was accompanied with the greatest con- 

 densation of volume, and the greatest disengagement of heat. 

 In composing this Dictionary, I calculated, for the first time, 

 the atomical constitution of the nitric acids employed by Mr. 

 Cavendish, for congelation ; and found with great satisfaction, 

 that the same proportion which had exhibited, in my experi- 

 ments, the most intense reciprocal action, as was indicated both 

 bv the aggregation of particles, and production of heat, was like- 

 wise that which most favoured solidification. Such acid congeals 

 at — 2'; but when either stronger or weaker, it requires a much 

 lower temperature for that effect. 



3. The next capital discovery in multiple proportions, was 

 made by M. Gay-Lussac, in ISOS, and published by him in the 

 second volume of the Memoires d' Arcueil. After detailing a 

 series of fine experiments, he deduces the following important 

 inferences : — " Thus it evidently appears, that all gases, in their 

 mutual action, uniforndy combine in the most simple propor- 

 tions ; and we have seen, in fact, in all the preceding examples, 



that 



