B.— CHEMISTRY. 89 
Similar experiments continued all through December with a holiday 
on Christmas Day.* Fused lead chloride, lead borate, and lead iodide 
gave confirmatory evidence, but the work was difficult and often gave 
inconclusive results. Faraday was anxious to extend it to the deposition 
of metals from aqueous solutions, and he found that zinc deposited on a 
platinum electrode gave an electro-chemical equivalent of 34:08, while 
the loss in weight of amalgamated zinc in contact with platinum compared 
with the weight of hydrogen evolved gave in two experiments equivalents 
of 30-2 and 32-31. ‘ Excellent,’ writes Faraday after the latter result. 
These researches had strengthened enormously the evidence for his 
First Law of Electrolysis— The Chemical power of a current of electricity 
is in direct proportion to the absolute quantity of electricity which passes ’ 
—and they had established the Second Law—‘ Electro-chemical equiva- 
lents coincide, and are the same with ordinary chemical equivalents.’ 
The paper itself is the most important of Faraday’s contributions to 
electrochemistry, and in it he summarises all his previous work. He 
begins by introducing the new terminology which he devised with the 
help of Whewell for the sake of greater precision of expression, and all 
his new names—electrode, anode, cathode, ion, anion, and cation, 
electrolyte and electrolysis—we use to-day with the significance which 
Faraday gave to them. After a short account of the conditions necessary 
for electro-chemical decomposition, he describes his new volta-electrometer 
and the evidence that led him to the conclusion that the amount of chemical 
action is dependent solely on the amount of electricity that passes through 
it. - He next discusses whether the products of electrolysis are primary or 
secondary, and gives his evidence for the identity of chemical and electro- 
chemical equivalents. He goes on to consider the absolute quantity of 
electricity associated with the particles or atoms of matter, pointing out 
how enormous this must be since 800,000 charges of a Leyden battery 
each one of which would suffice to kill a cat, “ would be necessary to supply 
electricity sufficient to decompose a single grain of water; or, if I am 
right, to equal the quantity of electricity which is naturally associated 
with the elements of that grain of water, endowing them with their mutual 
chemical affinity.’ Finally he speaks of the experiments in which he 
showed the equivalence of the hydrogen liberated and the zine dissolved 
when platinum and zinc amalgam are placed in contact in dilute acid. 
He writes: ‘ the results prove that the quantity of electricity which, being 
8 On December 19 no experiments are recorded, but a few extracts from the 
note-book show how busy he was, thinking and planning :— 
1192. ‘ With regard to intensity and its meaning, etc. Define intensity if possible 
and state its relation to quantity, time and conducting power.’ 
1195-1200. ‘ Nervous agency of Electricity.’ 
1207. ‘In the table I mean Real Electro chemical equivalents not hypothetical for 
we shall else outrun fact and lose the information directly before us. . 
must keep my researches really Experimental and not let them deserve anywhere 
the character of hypothetical imaginations.’ 
1212. ‘ Search for Fluorine by using a plumbago Pos. Pole acting on a fluoride.’ 
1213. ‘This process may finally give rise to some very good processes of analysis 
in determining weights or at least to some excellent modes of comparing weights 
of metals . . . a good principle of analysis for it will hold probably in salts as well 
if properly selected and may use mercury electrodes when convenient.’ 
A remarkable anticipation of modern methods of electrolytic analysis. 
