1814.] Scale of Chemical Equivalents. 1/J* 



that I seize the earliest opportunity to make it known to my readers 

 in general. It gives tl>e composition of any weight whatever of any 

 of the salts contained on the scale, the quantity of any other salt 

 necessary to decompose it, the quantity of new salt that will be 

 formed, and many other similar things, which are perpetually 

 occurring to the practical chemist, and cannot be answered without 

 an arithmetical calculation. I have used such a scale for above six 

 months, and found it attended with numberless advantages. I 

 cannot undertake to explain the instrument, either more clearly, or 

 in fewer words, than Dr. Wollaston has himself done in his own 

 paper. I conceive, therefore, that the best thing I can do is to 

 present my readers with the following extract from that paper, 

 which contains the most material part of it, as far as the explana- 

 tion of the instrument is concerned: — 



" It is not mv-design, in the table which follows this paper, to 

 attempt a complete enumeration of all those elements or com- 

 pounds which I suppose to be well ascertained, but merely to 

 include some of those which most frequently occur. 1 do not offer 

 it as an attempt to correct the estimates that have been formed by 

 others, but as a method in which their results may be advantageously 

 applied in forming an easy approximation to any object of our 

 inquiries. 



" The means by which this is effected may be in part understood 

 by inspection of the Plate [XXII.], in which will be seen the list 

 of substances intended to be estimated, arranged on one or the 

 other side of a scale of numbers in the order of their relative 

 weights, and at such distances from each other, according to their 

 weights, that the series of numbers placed on a sliding scale can at 

 pleasure be moved, so that any number expressing the weight of a 

 compound may be brought to correspond with the place of that 

 compound in the adjacent column. The arrangement is then such, 

 that the freight of any ingredient in its composition, of any reagent 

 to be employed, or precipitate that might be obtained in its analysis, 

 will be found opposite to the point at which its respective name is 

 placed. 



" In order to show more clearly the use of this scale, the Pl?te 

 exhibits two different situations of the slider, in one of which 

 oxygen is 10, and other bodies are in their due proportion to it, so 

 that carbonic acid being 2J':>4, and lime 35-4G, carbonate of lime 

 is placed at 63. 



" In the second figure, the slider is represented drawn upwards till 

 100 corresponds to muriate of soda; and accordingly the scale then 

 shows how much of each substance contained in the table is equi- 

 valent to loo of common salt. It shows, with regard to the diffe- 

 rent views of the analvsis of this salt, that it contains 46*6 dry 

 muriatic acid, and f..V ( of soda, or S9'8 sodium, and 13*6 oxygen; 

 or if viewed as chloride of sodium, that it contuini o"0-2 chlorine, 

 and 89 s sodium. With respect to reagent?, it may be seen that 

 $83 nitrate of lead, containing l'.»l of litharge employed to sepa- 



Voi. IV. N III. M 



