258 
ON THE VOLATILITY OF FIXED SALTS. 
very volatile natures, such as the chlorides of mercury, anti- 
mony, tin, bismuth, arsenic, iron, and zinc, are volatilized 
in considerable quantities, whilst those which are fixed, or 
but slightly volatile, as the chlorides of nickel, cobalt, cop- 
per, lead, and sodium, are carried up in but a small propor- 
tion. A similar effect takes place with the iodides ; but 
sometimes these products are decomposed, and the iodine is 
set free. The same observation is applicable to ammonia- 
cal salts, of which a few, such as the hydrochlorate and the 
carbonate, volatilize at a temperature under that of boiling 
water. Indeed, several acetates, butyrates, valerianates, 
and formates have given the same results. 
This property, which certain bodies possess of volatiliz- 
ing under the influence of the vapors of the liquids in which 
they are dissolved, has given rise to their application for 
several purposes, a few of which are of some importance. 
M. Larocque has also endeavored to render this property 
available, and the papers and designs which have been 
brought before you, seem to indicate that it may possibly 
be used with some advantage in the manufacture of paper 
hangings; but, it must also be said, that further trials will 
be necessary in order to arrive at a satisfactory practical 
result. 
It is by means of nitrate of silver that these papers were 
produced. Several other salts, under the same conditions, 
gave similar results, but neither of them answered the pur- 
pose so fully as the one we have just named. The follow- 
ing is the simple process employed by M. Larocque in the 
preparation of these papers. In a room in which some 
tables, or extended cords, are placed, some sheets of white 
paper are spread. In the centre of the room a porcelain 
capsule is placed on a furnace, and a mixture consisting of 
two pounds of nitric acid, sp. gr. 1.38, and one pound of 
water, to this is added about a pound of silver, and a gentle 
heat is applied. Action immediately takes place, giving 
rise to a considerable disengagement of binoxide of nitro- 
