538 
A PAPER ON ARSENICAL POISONS. 
more especially in the spongy form, the 
combination of these gases is very ra- 
pidly achieved, and, if mixed in the pro - 
portion, they are converted, usually 
with the phenomena of ignition, alto- 
gether into water. It is also well known 
and was first noticed by Dr. Turner, 
that if into an atmosphere of oxygen 
and hydrogen, mixed in the ratio neces- 
sary for forming water, certain other 
inflammable gases, such as carbonic, 
oxide and olefiant gas be introduced, 
the combination of the oxygen and 
hydrogen is, if not altogether suspend- 
ed, at least materially interrupted. This 
is what Dr. Henry denominates gaseous 
interference. The cause of this remark- 
able effect has, at different times, at- 
tracted the attention of eminent che- 
mists. Dr. Turner has ascribed it to 
the soiling of the platinum by the in- 
terferings, Dr. Faraday to some peculiar 
condition induced in the metal ; while 
Dr. Henry himself, at a period long 
prior to the present, conceived it to 
arise from the fact of carbonic oxide 
and olefiant gas, having a stronger 
affinity than hydrogen for oxygen gas. 
In his present paper. Dr. Henry in- 
vestigated the entire question. The pro- 
minent facts and inferences appeared to 
be that carbonic oxide retards and li- 
mits, but does not altogether prevent 
the action of platinum on the usual explo- 
sive mixture, and the same may be said 
of olefiant gas. The interfering power, 
however, of the former is vastly greater 
than that of the latter, their ratio being 
represented by the numbers 18 and 1. 
In the case of carbonic oxide, carbo- 
nic acid is always produced, the amount 
depending on the form of the platinum 
employed, the quantity of the inter- 
fering gas, and the temperature at 
which the experiment is conducted ; 
and, as a general rule, it may be laid 
down, that the interfering influence of 
the gas bears an inverse relation to the 
energy with which the platinum acts, 
and the degree of heat — conditions, 
however, which may be considered as 
identical. The diminution, and even 
disappearance, of interference at high 
temperatures. Dr. Henry attributes to 
a relative augmentation of the affinity 
of hydrogen for oxygen, an hypothesis 
indeed established by othery and inde- 
pendent facts. 
That Dr. Henry’s theory of gaseous 
interference is the true one he infers from 
the general fact of no gases exercising 
any such influence but those which 
have an affinity for oxygen ; and that 
it is strictly true, at least in the case of 
carbonic oxide there can be no ques- 
tion, seeing that some of the oxygen is 
actually employed in the production of 
carbonic acid. — Dr. Turner expressed 
his conviction of the value of Dr. 
Henry’s paper, of the ability with 
which it was drawn up, and of the cor- 
rectness of the solution of the problem 
of interference, and such appeared to be 
the prevailing opinion. — In the course 
of the paper several other interesting 
facts, of a collateral description, were 
stated, and, amongst others, that 
platinum causes, though slowly, the 
combination of a mixture of oxygen and 
carbonic oxide, but that the process is 
facilitated by the introduction into the 
jar of a little caustic potash. This latter 
circumstance he attributed to the re- 
moval of the carbonic acid by the potash 
as fast as it was produced, but Dr. Dau- 
beny, wdth much probability, viewed it 
as a case of disposing affinity. 
Mr. Herapath then read a paper on 
Arsenical Poisons, and drew the atten- 
tion of the Section to the case of Mrs. 
Burdock,, in which he he was profes- 
sionally employed, and which proved to 
be one of Realgar. While engaged in 
chemical investigations connected with 
this case, he ascertained that Realgar is 
convertible into orpiment by hydrosul- 
phuric acid, and the soluble hydrosul- 
phates, and that it undergoes, as might 
have been anticipated, an analogous 
change in animal bodies submitted to 
putrefaction. Mr. Herepath also stated, 
if we understood him rightly, that Real- 
gar favours the conversion of animal mat- 
ters into adipocire, a fact, undoubtedly 
of a very novel description, and one not 
very reconcileable with those researches 
of Chevreul and Gay-Lussac, which 
have demonstrated this fatty substance 
to be an ammoniacal soap. This gentle- 
man concluded by exhibiting some ex- 
periments illustrative of his methods of 
toxicological investigation. 
Section C.— GEOLOGY AND GEO- 
GRAPHY. 
Dr. Buckland in the chair. — ^The first 
paper was. A Classification of the old 
Slata Rocks of Devonshire, and on the 
true position of the Culm deposits of 
the central portion of that country,’ by 
