Feb, 2, 1871] 
NATURE 

Its shortcomings led to the invention of another process by 
Gay-Lussac, known as the volumetric, or humid, method, which 
is much more accurate, and is now practised very generally on 
the Continent. Its principles were briefly glanced at. Its in- 
troduction, however, into the Indian Mints was not considered 
desirable by their assay officer for certain reasons, a few of which 
were given. The method of cupellation, therefore, being not 
accurate enough for the purposes of buying and selling bullion, 
and that by the French process being considered not well suited 
to Indian Mints, it became necessary to look out for and intro- 
duce into the Mints of this country a process more likely to 
answer all the ends in view. 
This object was attained by the adaptation and introduction of 
the process now in use, viz. the ‘‘ Chloride process of assaying 
silver.’ Hitherto it had never been resorted to, except on a 
very small scale. Assayers appear to have shrunk from the 
manifest difficulties of manipulation in collecting, drying, and 
weighing the precipitated chloride of silver. The credit is due 
to Mr. James Vodd, a former Assay Master of the Calcutta 
Mint, of having so simplified, modified, and systematised the 
details of this method, as to render its application to the assay- 
ing of silver on a large scale easy and accurate. The principles, 
and an outline of the details of the process were then given, an 
understanding of some of the chief appliances and steps in the 
manipulations being assisted to by suitable photographs. The 
system of weights in use, and the quantity of the sample taken 
for assay, were also explained, as well as the points wherein 
this system might fairly be considered better suited toa Mint in 
India than the other methods. 
In conclusion Dr. B. alluded to the vast amount of silver 
bullion which this process enabled the assay officers of the 
Indian Mints to deal with confidently and accurately during the 
past fifteen years. In one year alone, that of 1865-66, the im- 
portation of silver bullion reached to the immense amount of 
over fourteen millions sterling, so putting to a crucial test the 
system of assay used for its valuation. 


SOCIETIES AND ACADEMIES 
LoNDON 
Royal Society, January 12.—‘‘ On Fluoride of Silver,” Part 
Il.. by George Gore, F.R.S. An exhaustive account of the 
behaviour of argentic fluoride in vessels of platinum, carbon, 
and various fluorides in contact with chlorine, bromine, and 
iodine at various temperatures. When argentic fluoride is com- 
pletely decomposed by chlorine in platinum vessels at a red heat, 
the reaction agrees with the following equation :— 
4 Ag F+4Cl+Pt=4AG Cl, Pt Fy. 
Vessels of cryolite and of fluor-spar were found incable of re- 
taining argentic fluoride in a melted state. Other vessels were 
also made by melting and casting various mixtures of earthy 
fluorides at a high temperature ; and although forming beautiful 
products, probably capable of technical uses, they were not 
capable of retaining silver fluoride in a state of fusion. Numerous 
vessels were also made of seventeen different fluorides by mould- 
ing them in the state of clay and baking them at suitable temper- 
atures; these also were found incapable of holding melted 
fluoride of silver. Argentic fluoride was only superficially de- 
composed by chlorine at 60° Fahr. during thirty-eight days. 
When heated to 230° Fahr. during fifteen days in a platinum 
vessel in chlorine, it was very little decomposed. Chloride of 
silver heated to fusion in a platinum vessel in chlorine corroded 
the vessel and formed a platinum-salt, as when fluoride of silver 
was employed. An aqueous solution of argentic fluoride agitated 
with chlorine evolved heat and set free oxygen, in accordance 
with the following equation :— 
8 AgF+8Cl+H,O=5 AgCl +3 AgClO+ 8HF+0, 
or 
7 AgCl+AgClO,+8HF+0. 
Dry hydrochloric acid gas completely decomposed argentic fluo- 
ride in a melted state, but only acted upon it superficially at 60° 
Fahr. A saturated aqueous solution of argentic fluoride was 
not precipitated by chloric acid. Perfectly anhydrous fluoride of 
silver was only superficially decomposed by contact with bromine 
in a platinum vessel during thirty-six days at 60° Fahr., or during 
two days at 200° Fahr. At a low red heat in vessels of platinum 


277 
argentic fluoride was completely decomposed by a current of 
bromine vapour, a portion of its fluorine being expelled and a 
portion corroding the platinum and forming an insoluble com- 
pound of fluoride of platinum and bromide of silver. In carbon 
boats at the same temperature the whole of the silver-salt was 
converted into bromide, the boat being corroded and the fluorine 
escaping in chemical union with the carbon. The action of 
bromine on an aqueous solution of argentic fluoride was similar 
to the action of chlorine. A solution of argentic fluoride yielded 
copious precipitates both with hydrobromic and bromic acids, 
Under the influence of a temperature of 200° to 600° Fahr. in 
closed platinum vessels, iodine very slowly and incompletely de- 
composes argentic fluoride without corroding the vessels, and 
produces a feeble compound of argentic iodide, fluorine, and 
iodine, from which the two latter substances are expelled at a 
red heat. At a red heat in platinum vessels, iodine produces 
argentic iodide, and in the presence of free argentic fluoride cor- 
rodes the vessels in consequence of formation of platinic fluoride ; 
iodine and fluorine pass away together durirg the reaction. In 
vessels of carbon at the same temperature, argentic iodide is 
formed, the vessels are corroded, and a gaseous compound of 
fluorine and carbon is produced. By treating an aqueous solu- 
tion of argentic fluoride with iodine, similar results are produced 
as with bromine and chlorine ; a similar solution yields copious 
precipitates both with hydriodic and iodic acids. A mode of 
analysis of iodine is also fully described in the paper. A known 
weight of iodine was dissolved in absolute alcohol, a strong solution 
of argentic nitrate of known strength added to it in proportions at 
a time with stirring until the colour of iodine exactly disappeared. 
The mixture was evaporated, the free nitric acid expelled by 
careful heat, and the residue weighed. The residue was then 
heated to fusion to convert the iodate of silver into iodide, and 
again weighed. ‘lwo experiments of this kind yielded accurate 
results, and the process was easy and expeditious. 
January 19.—‘‘On the Structure and Development of 
the Skull of the Common Frog (Kana temporaria),” by W. 
Kitchen Parker, F.R.S. At the close of my last paper, 
“On the Skull of the Common Fowl,” I spoke of bring- 
ing before the Royal Society another, treating of that of the 
osseous fish, I was working at the early conditions of the sal- 
mon’s skull at the time. 1 was, however, led to devote my 
attention to another and more instructive type early in the fol- 
lowing year; for it was then (January 1869) that Professor 
Huxley was engaged in preparing his very important paper ‘‘ On 
the Representatives of the Malleus and Incus im the other Verte- 
brata” (see Zool. Proc. May 27, 1869). In repeating some of 
his. observations for my own instruction, it occurred to me to 
renew some researches I had been making from time to time on 
the frog and toad. The results were so interesting to us both, 
that it was agreed for me to work exhaustively at the develop- 
ment of the frog’s skull before finishing the paper on that of the 
salmon. On this account Professor Huxley mentions in his paper 
(of. ct, p. 406) that he leaves the Amphibia out of his de- 
monstration, and that they are to be worked out by me. The 
amount of metamorphosis demonstrable in the chick whilst 
enclosed in the egg, suggested a much more definite series of 
changes in a low, slow-growing Amphibian type. I think that 
this has been fully borne out by what is shown in the present paper. 
The first of the ten stages into which I have artihcially divided 
my subjeet is the unhatched embryo, whilst its head and tail pro- 
ject only moderately beyond the yelk-mass. Another stage is 
obtained by taking young tadpoles on about the third day after 
they have escaped from their glairy envelope ; a few days elapse 
between the second and third stages, but a much longer time 
between the third and fourth, for the fourth stage is the perfect 
tadpole, before the limbs appear and whilst it is essentially a fish 
with mixed Chimeroid and Myxinoid characters. Then the 
metamorphosing tadpole is followed until it is a complete and 
nimble frog, two stages of which are examined, and then old 
individuals are worked out, which give the culminating characters 
of the highest type of Amphibian. 
The early stages were worked out principally from specimens 
hardened in a solution of chromic acid ; and the rich umber- 
biown colour of these preparations made them especially fit for 
examination by reflected light. 
Without going further into detail as to the mode of working 
my subject out, and without any lengthened account of the 
results obtained, I may state that the following conclusions haye 
been arrived at, namely, that the skull of the adult is highly 
compound, being composed of ;— i 

