1813.] Proceedings of Philosophical Societies. 463 



Article XI. 



Proceedings of Philosophical Societies. 



ROYAL SOCIETY. 



The Royal Society resumed its meetings on Thursday, the 4th 

 of November. A description of a sliding scale of chemical 

 equivalents, contrived by Dr. Wollaston, was read. This con- 

 trivance is distinguished by all that sagacity which characterizes 

 Dr. Wollaston, and cannot but be highly useful to the practical 

 chemist. It is not easy to render the nature of this contrivance 

 intelligible without an engraving, which I do not consider myself 

 at liberty to give before the publication of the paper in the Phi- 

 losophical Transactions ; but the following observations will 

 perhaps suggest some idea of it to those who are interested in 

 practical chemistry. 



It was first observed by Richter that when two neutral salts are 

 made to decompose each other, the neutrality of neither is dis- 

 turbed. Thus if you dissolve 100 grains of sulphate of potash 

 in water, and pour into the solution muriate of barytes in suffi- 

 cient quantity to decompose the whole of the sulphate, two new 

 neutral salts will be formed, namely, sulphate of barytes and 

 muriate of potash. If into the muriate of potash thus formed a 

 sufficient quantity of nitrate of silver be dropped to decompose 

 it, two new neutral salts will be formed, namely, nitrate of 

 potash and muriate of silver. Thus the same weight of jxjtash 

 has been united in succession with sulphuric, muriatic, and nitric 

 acids. The weight of barytes that neutralized the muriatic acid 

 neutralized likewise the weight of sulphuric acid combined with 

 the potash which had neutralized the sulphuric acid. These 

 observations of Richter were still farther generalized by Ber- 

 thollet ; but it is to Dalton that we owe the full generalization 

 of the facts, and the explanation of them. He supposes that 

 bodies unite atom to atom, and showed how the weights of the 

 atoms of bodies might be determined. This subject, having 

 been already explained at considerable length in the Annals of 

 Philosophy, need dot be farther insisted on here. 



Dr. Wollaston ha* divided the slider of a scale into the loga- 

 rithmic (paces from 10 to 820, by a method familiar to all who 

 are acquainted with the nature of logarithms, or in a similar 

 manner as the line of numbers is laid down in Gunter's scale. 

 1 !<• considers 10 as representing the weight of an atom of oxygen. 

 On both sides of the scale he has written the substances most 

 familiar to chemists, viz. the acids, bases, water, and principal 

 -alt?, each opposite to the number on the slide, which corre- 



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