632 
TO COB/RESPONDENTS. 
BOOKS RECSIVEB. 
Asiatic Cholera. By F. A. Burrall, M.D. New York : William Wood and Co., 61, 
Walker Street. Svo, pp. 155. 18G6. (From the Publishers.) 
On the Safe Abolition or Pain in Labour and Surgical Operations, by Anaes¬ 
thesia with Mixed Vapours. By Robert Ellis. London: Robert Hardwicke, 
192, Piccadilly. I860. 
On the Use of the Sphygmograph in tiie Investigation of Disease. By Bal¬ 
thazar W. Foster, M.D., etc. London: printed by T. Richards, 37, Great Queen 
Street. (From the Author.) 
TO CORRESPONDENTS. 
Persons having seceded from this Society may be restored to their former status on 
payment of arrears of subscription and the registration fee of the current year. 
.Those who were Associates before the 1st of July, 1842, are privileged (as Founders 
of the Society) to become Members without examination. 
An Improver. —(1) The retail trade would be preferable. (2) ‘ Ure’s Dictionary of 
Arts, Manufactures,’ etc. 
B. P .— Volumetric Test Solutions .—The use of iodine as a volumetric test solution is 
founded upon the formation of hydriodic acid (HI). An atom of iodine takes the re¬ 
quired hydrogen from an atom of sulphuretted hydrogen. A similar result is also ob¬ 
tained when the solution of iodine is added to solution of sulphurous acid, in which case 
SOo is converted into S0 3 by decomposing water, the hydrogen of which is taken by the 
iodine, and the oxygen by the sulphurous acid, and, as this acid requires only one atom 
of oxygen to convert it into S 0 3 , the change is represented by one atom of iodine. In 
using the solution of iodine for the estimation of arsenious acid, the reaction is similar, 
but here the arsenious acid (As0 3 ) is converted into arsenic acid (AsO s ), for which two 
atoms of oxygen are required, involving the use of two atoms of iodine ; therefore, the 
iodine that corresponds to the conversion of an atom of sulphurous into sulphuric acid 
will effect the conversion of only half an atom of arsenious into arsenic acid. 
In the use of nitrate of silver for estimating hydrocyanic acid, as described in the 
Pharmacopoeia, the acid is first neutralized with soda, and, on adding nitrate of silver to 
this, a soluble double salt is formed consisting of cyanide of sodium and cyanide of silver, 
in which one atom of silver represents two atoms of cyanogen or hydrocyanic acid. 
The other cases alluded to are similarly explained. 
Vindex. —Peroxide of potassium is best prepared by submitting fused potassium to the 
action of a regulated current of dry air, and afterwards of oxygen gas at a moderate 
temperature. 
Inquirer (Torquay).—Apply by letter to Professor Bentley, 17, Bloomsbury Square, 
giving name and address. 
Apprentice (Lincoln).—Bentley’s ‘Manual of Botany,’ price 12s. 6c/. 
W. J. 11. (Manchester) wishes for the formula for “Halley’s Acid Solution.” 
G. R. L. S. (Langborne).—(1) The work itself. (2) Uncertain—probably during 
the present year. (3) Yes. 
“Medicos” (Bristol).— Syrvpus Ferri Superphosph. c. Calce. Vol. i. (2nd series) 
p. 498. 
Instructions from Members and Associates respecting the transmission of the 
Journal before the 25th of the month, to Elias Bremridge, Secretary, 17, 
Bloomsbury Square, W.C. 
Advertisements (not later than the 23rd) to Messrs. Churchill, New Bur¬ 
lington Street. Other communications to the Editors, Bloomsbury Square. 
