54 On Sir Benjamin Brodie' s " Ideal Chemistry " 



the only exception having reference to that which concerns hy- 

 drogen. With regard to hydrogen, which is thus in an alto- 

 gether peculiar predicament, the rule for deducing the coefficient 

 of u (the Brodie-symbol for hydrogen) from the old formula is 

 this. Add to the numberof atoms of hydrogen in the old formula 

 one for each atom of chlorine or other halogen or nitrogen, &c, 

 and divide the sum by 2, and the result will be the appropriate 

 coefficient for a, 



There is just one other difference between the new and the 

 old formulae, viz. in the new formulae the arrangement of sym- 

 bols is alphabetic according to the order of the Greek alphabet. 



As Sir B. Brodie says, he might have represented the unit-vo- 

 lume of hydrogen by a 2 , i, e. the standard litre of hydrogen by 

 a 2 instead of by u, as he has actually done. Had he done so, 

 the new formulae would have been absolutely the old formulae 

 translated into Greek, and we may add, would have been in ac- 

 cordance with the facts of the science. 



Sir B. Brodie has chosen, for reasons which he does not dis- 

 close, to represent the molecule and the atom of hydrogen as 

 identical. As a consequence of this mode of representation he is 

 straightway landed at the discovery that chlorine itself is a che- 

 mical compound of hydrogen. 



The following is no misrepresentation of the reasoning by 

 which this conclusion is reached : — 



The least quantity of hydrogen which can exist in my ideal 

 world of litres is one litre of hydrogen weighing 0*089 grm., 

 and a litre of a compound gas, if it contains any hydrogen at all, 

 must contain not less than 0-089 grm. of hydrogen. A litre of 

 hydrochloric acid gas certainly contains hydrogen, for we can 

 extract hydrogen from it; therefore it must contain at least 

 0*089 grm. of hydrogen. 



Now our modern chemical analysis extracts from a standard 

 litre of hydrochloric acid gas 0-0445 grm. of hydrogen, and also 

 another substance which we call chlorine, and presume to be an 

 element. But matter is never lost, and therefore the chlorine 

 extracted from the hydrochloric acid must contain the missing 

 0*0445 grm. of hydrogen. 



In conclusion we beg to offer our congratulations to Sir B. 

 Brodie that he has taken for the modulus of his system the sym- 

 bol of hydrogen. Suppose, in an evil hour, he had taken f as 

 the modulus, and made f the symbol of the operation by which 

 the unit of space is converted into the unit of oxygen (chemists 

 have before now been misguided enough to make oxygen their 

 standard, we instance the Tables of equivalents wherein oxygen 

 = 100). Mark the consequences which Sir B. Brodie has 

 escaped. The litre of oxygen £ is the least quantity of oxygen 



