422 
BATH CHEMISTS’ ASSOCIATION. 
copper as an acidimetric solution), that of cyanides by means of silver, and of chlorides- 
by nitrate of mercury in the presence of urea. I will shortly describe the former, as it 
is of especial interest to the pharmaceutist as giving the means of estimating the strength 
of HCy and the amount of that acid in bitter-almond and cherry-laurel water, and also 
the value of the commercial cyanides of potassium. This beautiful and exact volumetric 
method was devised by Liebig, and depends on the fact that AgCy forms a double salt 
with KCy which is soluble in water; the slightest excess of silver, however, decomposes 
this and insoluble AgCy is precipitated. If, therefore, standard silver solution be added 
to an alkaline cyanide, no precipitation takes place till sufficient has been used to combine 
with half of the Cy present, the other half remaining in combination with the potash and 
forming the soluble double salt. As soon as this point is reached, the next drop of silver 
causes a precipitation of AgCy. One equivalent of silver used thus indicates two equiva¬ 
lents of Cy present. We may express this perhaps rather differently, and say that so¬ 
lutions of silver give with alkaline cyanides a white precipitate of AgCy, which is soluble 
in the cyanide either of potassium or sodium, as the case may be. When, therefore, 
the cyanide present is decomposed by the silver, it can no longer dissolve the AgCy, 
and a precipitate results. The law of equivalents teaches us that the exact point occurs 
when half the cyanide is decomposed and thus the whole amount present is readily 
ascertained. 
I am well aware that the slight sketch of the leading features of volumetric analysis 
I have thus brought before you is a very imperfect one, and that it contains nothing 
new or original. I am also assured that many here are as well acquainted with the 
subject as I am. These will, I hope, bear with what will have been a dull evening to 
them, while they consider what I take to be an important part of the work of such asso¬ 
ciations as this,—the diffusion of useful knowledge among our younger members and 
associates, no less important than the mutual interchange of information on original 
subjects. I will therefore hope that even the cursory description now offered may have 
the effect of leading some to study further, and above all, to practise this beautiful and 
useful branch of analysis. 
Mr. G. Ward, F.C.S. remarked that the paper to which they had listened with so much 
pleasure, could not fail to be practically useful to every one present. The introduction 
of materials for volumetric analysis into the British Pharmacopoeia made the present 
communication especially opportune and acceptable. With reference to the six processes 
selected for admission into the British Pharmacopoeia, he thought that with one ex¬ 
ception, they all were deserving of confidence, as being processes in which the termina¬ 
tion of the operation was sharply defined, and this was the first essential of a good 
method of volumetric assay. He thought that the bichromate of potash test for iron 
was often unsatisfactory in the hands of beginners, from doubts as to when the operation 
was over. The permanganate appeared to be preferable. He moved that the hearty 
thanks of the Association be given to the author of the paper. 
Mr. Atkixson seconded the motion, which was carried by acclamation. 
Mr. Reynolds exhibited some specimens which had been kindly lent by the Mag¬ 
nesium Metal Company (Limited), of Manchester. They included fine masses of the 
metal both in its crude and distilled state. Three forms of lamp that have been used 
for burning the wire or ribbon were also shown. Although the reflectors attached to 
these condense the light, the rapid combustion of the metal leaves much to be accom¬ 
plished towards ensuring its steady consumption. The pure whiteness as well as intensity 
of the light was well shown by illuminating with it sheets of paper toned yellow, blue, or 
green, which colours could be distinguished as well as by daylight. 
HATH CHEMISTS’ ASSOCIATION. 
There has been a branch of the Pharmaceutical Society in Bath since the formation 
of that Society, and in its early days it was one of the most flourishing offsets of the 
parent stem ; but for many years it has been in a languishing state, and no meetings had 
been held amongst the chemists of Bath until the then approaching meeting of the 
Pharmaceutical Conference in our city called the chemists together, and there was 
formed, as a temporary association, the Bath Branch of the British Pharmaceutical Con- 
