Sulphate of soda. Sparts From 50o to 0o.
Muriatic acid

5

Snow or pounded ice 2 parts From 0° to 5o.

Muriate of soda

1

TABLE OF FREEZING MIXTURES CONTINUED.

Mixtures.

Thermometer sinks.

Dilut. sulphuric acid 10 parts From-68o to-91°.

Snow

8

Nitrate of ammonia 1 part From 50° to 4o.

Water

Nitrate of ammonia
Carbonate of soda

Water

1

1.

MANAGEMENT OF THE PRECEDING MIXTURES FOR PRODUCING COLD.

To produce the effects before stated, the salts must be reduced to powder, and contain their full quantity of water of crystallization. The vessel in which the freezing mixture is made should be very thin, and just large enough to hold it; and the materials should be mixed together as expeditiously as possible, taking care to stir the mixture at the same time with a rod of glass or wood.

In order to obtain the full effect, the materials ought to be first cooled to the temperature marked in the table, by introducing them into some of the other frigorific mixtures, and then mingling them together in a similar mixture. If, for instance, we wish to produce = 46°, the snow and diluted nitric acid ought to be cooled down to 0°, by putting the vessel which contains each of them. into the fifth freezing mixture in the above table before they are mingled together. If a more intense cold be required, the materials to produce it are to be brought to the proper temperature by being previously placed in the second freezing mixture.

This process is to be continued till the required degree of cold has been procured.

SECT. IX.

CONVERSION OF SOLIDS AND FLUIDS INTO THE AERIFORM OR GASEOUS STATE.

We have seen before that in order to render solids fluid, a certain quantity of caloric is necessary, which combines with the body, and therefore cannot be measured by the thermometer; we shall now endeavour to prove, that the same holds good in respect to the conversion of solids or fluids into the vaporous or gaseous state.

CONVERSION OF SOLIDS INTO THE GASEOUS STATE.

EXPERIMENT I.

Take a small quantity of carbonate of ammonia, introduce it into a retort, the neck of which is directed under a cylinder filled with mercury and inverted in a basin of the same fluid. On applying heat to the body of the retort, the carbonate of ammonia will be volatilized, it will expel the mercury out of the cylinder, and become an invisible gas, and would remain so, if its temperature was not lowered.

The same is the case with benzoic acid, camphor, and various other substances.

SECT. X.

CONVERSION OF FLUIDS INTO THE GASEOUS STATE.

All fluids may, by the application of heat, be converted into an aeriform elastic state.

When we consider water in a boiling state, we find that this fluid, when examined by the thermometer, is not hotter after boiling several hours than when it began to boil, though to maintain it boiling a brisk fire must necessarily, be kept up. What then, we may ask, becomes of the wasted caloric? It is not perceptible in the water, nor is it manifested by the steam; for the steam, if not compressed, upon examination, is found not to be hotter than boiling water. The caloric is therefore absorbed by the steam; and although what is so absorbed is absolutely necessary for the conversion of water into the form of steam, it does not increase its temperature, and is therefore not appreciable by the thermometer.

This conclusion is further strengthened by the heat given out by steam on its being condensed by cold. This is particularly manifested in the condensation of this fluid in the process of distilling, where, upon examining the