114 On Chemical Equivalents. 



Now we must find such an assemblage of the primes or atoms 

 of these elements, as will form a sum-total of 7'5; and at the 

 same time be to each other, in ihe above proportions. The fol- 

 lowing very simple rule will give a ready approximation ; and by 

 a common sliding scale, it may be worked by inspection. 



Multiply each proportion per cent, by the compound prime, 

 and compare the products with the multiples of the constituent 

 primes. You can then estimate the number of each prime re- 

 quisite to compose the whole. Thus, 



Theorv. Exp. 

 0-lCSx 7-5:= 1-2600 or 10 hydrogen = 1-25 167' 16-8 

 0-283 X 7-5 = 2-1 22.5 3 carbon =2-25 30-0 28-3 



0-549x7-5=4-1175 4 oxygen =4-00 53-3 54-9 



7-50 1000 100-0 



The differences between these theoretical and experimental 

 proportions, are probably within the limits of the errors of the 

 latter, in the present state of analysis. 



If on Dr. Wollaston's scale, we mark with a type or a pen, 

 2h, 3h, &;c. up to lOh; 2c, 3c, 4c, 5c; and 2n, 3n, 4n ; re- 

 spectively opposite to twice, thrice, &c. the atoms of hydrogen, 

 carbon, and nitrogen, as is already done for oxygen (with the 

 exception of the fourth, where copper stands) we shall then have 

 ready approximations to the prime components, by inspection of 

 the scale. Move the sliding part, so that one of the quantities 

 per cent, may stand opposite the nearest estimate of a multiple 

 prime of that constituent. Thus we know that hydrogen, car- 

 bon, and oxygen, bear the relation to each other of 1, 6, 8; and, 

 of course, the latter two, that of 3 to 4. But 54-9 oxygen, be- 

 ing more than one-half of 100, the weight of oxygen in the 

 compound prime is more than the half of 7*5, and therefore 

 points to 4. Place 54-9 opposite 4 oxygen (where copper stands) 

 we shall find 18 opposite 10 hydrogen, and 30-7 opposite 3 car- 

 bon. Here we see the proportions of carbon and hydrogen, are 

 both greater than by Vauquelin's analysis. Try 51 opposite 

 4 oxygen, then opposite 3 carbon we have, 28-7, and opposite 

 10 hydrogen 16-'). The proportions I have calculated arithme- 

 tically above, seem somewhat better approximations ; they were 

 deduced from hydrogen 0-125, and carbon 0-75, instead 0132 

 and 0-754, as on the scale. 



If the weight of the compound prime is not given, then we 

 must proceed to estimate the nearest prime proportions, after 

 inspection of those per cent. The scale may be used with ad- 

 vantage, as just now explained. 



The following case has been reckoned difficult of solution, and 

 has been even involved in an algebraic formula. Let us suppose 



a vege- 



