626 SHEFFIELD PHARMACEUTICAL AND CHEMICAL ASSOCIATION. 
inverting over a watcli-glass containing the fluid a second one having a single drop of 
the silver nitrate on the inner surface. A white film will soon form from the vapour 
of hydrocyanic acid present. Another elegant test is to form sulphocyanide of am¬ 
monium by presenting a drop of yellow sulphide of ammonium to the action oi the 
vapour. The reaction of this salt with persalts of iron, producing a crimson red 
colour, is well known, and is distinguished from the red colour produced by meconic 
acid and persalts of iron, by its ready removal on the addition of mercuric chloride, 
which has no action upon the colour of the meconate. 
“ In a second portion of the liquid or substance to be examined, search may be 
made for oxalic acid, and the mineral acids and salts. 
“ Powdered substances may often be readily detected by projecting a portion into 
a tall vessel filled with water. Any white particles may be picked out and examined 
for arsenic, lead, etc. Others of red, yellow, or green colour, may be arsenic, copper, 
antimony, etc. 
“ A third portion should next be acidified with hydrochloric acid, and one-third of 
it taken for the detection of the alkaloids. A description of the methods employed 
was given, and the special tests for strychnia, brucia, morphia, and meconic acid 
shown. The microscope is invaluable for the certain identification of crystalline pre¬ 
cipitates, as shown in Wormley’s ‘Micro-chemistry of Poisons,’ which was highly 
recommended. 
“ In the next portion the metallic poisons, arsenic, antimony, and mercury are to 
be sought. All precipitate in the metallic state from an acidified solution upon im¬ 
mersion of a piece of clean copper foil. The characters of the sublimates from these 
deposits was described, as well as the method of applying Marsh’s test for arsenic. 
Lead, copper, and zinc are to be detected in the last portion.” 
The President, Mr. E. Wilson, proposed, and Mr. Ward seconded, “that the best 
thanks of the meeting be given to Mr. Baker for his able and interesting lecture,” which 
was carried unanimously. 
The minutes of the last meeting having been read and confirmed, the Secretary 
read a letter he had received from Professor Attfield, thanking the Association for 
having elected him one of its Honorary Members. 
Mr. Cocking proposed and Mr. Ward seconded, that the letter be entered upon 
the minutes. Carried. 
The nomination and election of members and associates concluded the business of 
the meeting. 
The Second General Monthly Meeting was held in the rooms, March 9th, Mr. 
Wilson, the President, in the chair. 
A lecture upon Disinfectants was delivered by A. H. Allen, Esq., E.C.S., and Lec¬ 
turer at the Sheffield School of Medicine. He said that modern medical science had 
proved that infectious diseases, such as cholera and typhus fever, owed their origin to 
the presence of minute germs or organized cells which multiplied with extreme 
rapidity under favourable conditions. These germs were solid, and probably acted in 
a similar manner to the yeast plant in presence of sugar or bread. In disinfecting, 
therefore, we should keep in view the necessity of destroying the deadly germs, be¬ 
sides simply getting rid of a disagreeable smell. There were some substances, such as 
chloride of lime, which acted chiefly on the smells, and were little better than deodo¬ 
rizers, unless used in large excess ; while others, like carbolic acid, were real anti¬ 
septics, killing the germs and arresting all putrifaction, but exerting little or no action 
upon the smells. In choosing a disinfectant, it was necessary to be guided, to a 
certain extent, by circumstances, but on no account to use two disinfectants together, 
which will eventually destroy each other’s action ; such, for instance, as chloride of 
lime and Macdougall’s Disinfecting Powder. Mr. Allen concluded by exhibiting 
some of Dr. Tyndall’s beautiful experiments upon the dust of the air, proving the 
motes, visible in a strong light, to consist of organized matter, capable of removal 
by filtering the air through cotton wool, or passing it through a red-hot tube. 
Mr. Dobb proposed, and Mr. Ward seconded, that a vote of thanks be awarded to 
Mr. Allen for his lecture, which was unanimously carried. 
