4 Definite Proportions. 
dies respectively. Thus the quantity of B is to that of A, 
as 2 to 1; to that of C, as 2to 3; and to that of D, as 2 to 
4. We might extend the number of elements fo one hun- 
dred, or one thousand, and we should still find the same cu- 
rious law obtaining ; namely, that when any two, or three, or 
even the whole number of the series, entered into combina- 
tion, their respective quantities would be in the same ratio to 
each other, as the numbers attached to them as equivalent 
quantities.* 
The utmost facility of calculation is imparted to the sub- 
ject of chemical combinations and decompositions, by Dr. 
Wollaston’s Scale of Chemical Equivalents. If a series of 
numbers, beginning with 10 and increasing by 1, be written 
under each other at such distances that the intervening spaces 
1:2. Now, if we write opposite to the numbers on this 
scale, the bodies of which the numbers themselves are the 
equivalents, then the distances between these bodies will, in 
ike manner, be the measures of the ratios of their combining 
quantities, and will be the same with the distances between 
the numbers. So far the seale amounts to little else than a 
synoptic table of chemical equivalents ; but the excellence of 
this arrangement is, that by means of the slide, we can in- 
stantaneously solve a great number of cases which arise out 
of combinations and decompositions, the solution of which, 
in the ordinary way, would require a tedious number of com- 
putations. Without moving the slide, the scale tells us that 
the equivalent of common salt (Muriate of Soda) omitting 
fractions, is 74—thet it consists of 34 parts of muriatic acid, 
and 40 of soda ; and that if we would decompose 74 grains of 
opposite to their respective bodies, because all these are 
*The smallest quantities capable of entering inte combination are here 
understood. - = 
