CHEMICAL NOTATION AND ATOMIC WEIGHTS. 
7 
in measure for a given quantity, and let each call that same quantity in its own way; 
and if even Brother Jonathan, who more generally speaks our language than any other, 
is determined not to call a box a box, let him use any other word that pleases him 
better, and we will understand him. America and England coming into the Continental 
metric system, would make its use nearly universal in the commercial world. 
With regard to the time in which this change should become law, I cannot see the 
need for long delay, any more than in other enactments which are passed and at once 
become law. In a change of weights and measures, you have only to establish the 
standard, and commercially the price will regulate itself. The general community, and 
especially the poorer classes, will have their difficulties done for them, and the educated 
will find it infinitely easier than the juvenile competitive examination for the civil ser¬ 
vice at present established. I do therefore hope the favourable progress this subject has 
made on its second reading will be so much gained towards its final accomplishment. 
Mr. Shaw moved a vote of thanks to the President for his able address, and passed a 
high encomium on the efficient and constant manner in which he had filled the Presi¬ 
dent’s chair during the Session. 
Mr. Redford seconded the motion, which was carried unanimously by acclamation. 
ORIGINAL AND EXTRACTED ARTICLES. 
ON RECENT CHANGES IN CHEMICAL NOTATION AND 
ATOMIC WEIGHTS. 
BY WILLIAM A. TILDEN, F.C.S., DEMONSTRATOR IN THE LABORATORY OF 
THE PHARMACEUTICAL SOCIETY. 
{Concludedfrom Vol. IX. page 583.) 
We are indebted mainly to Gerhardt for the theory of types. In four sub¬ 
stances which he selected, viz. hydrogen, hydrochloric acid, water, and am¬ 
monia, he saw models or ‘ types ’ of structure upon which he conceived the 
formulae of all other bodies should be moulded. The analogy really extends 
beyond the formulae to the properties of the bodies. Had it been otherwise, the 
idea would have fallen to the ground. It has, however, been extended and modi¬ 
fied, and the principle upon which it is founded furnishes the basis of modern 
rational formulae. My purpose is not to show the objections which have been 
urged against the type formulae and the manner in which they have been met, 
but simply to explain the notation now in use among a large number of emi¬ 
nent chemists. 
This purpose will best be served by writing the rational formulae of one or 
two compounds of importance, and giving the reasons which have led to this 
particular mode of expression. 
There are two kinds, it may be said, of rational formulae commonly em¬ 
ployed. 
Referring to acids, for example, we are usually satisfied with denoting 
them by such formulae as to keep prominent the characteristic property of 
compounds of that class, viz. that of exchanging one or more atoms of 
hydrogen for an equivalent quantity of a metal, by the ordinary way of 
double decomposition. 
Formula. 
Old. New. 
Hydrochloric Acid.HC1 .... II Cl 
Nitric Acid.HO, N0 5 . . . HN0 3 
Acetic Acid.HO, C 4 H 3 0 3 . HC 2 H 3 0 2 
Sulphuric Acid.HO, S0 3 . . H 2 S0 4 
Tartaric Acid.2HO,C 8 H 4 O ie , . H 2 C 4 H 4 0 6 
Phosphoric Acid.3HO,PO s . . H 3 P0 4 
