The following selection of mixtures causing various degrees of cold,
the starting point of the cooling being indicated in the first column,
will probably serve many purposes. It should be stated that the amount
of depression in temperature will practically be the same, even if the
temperature to start from is higher. Of course in the case of snow it
cannot be higher than 0° C. (32° F.) But in some cases it is necessary
to start at a temperature below 0° C. For instance, the temperature of
-49° C. may be reached by mixing 1 part of snow with ½ part of dilute
nitric acid. But then the snow must have the temperature -23° C. If it
were only at 0° C., the depression would be only to about -26° C.:
_________________________________________________________________
|
| The temperature sinks
Substances to be mixed in parts by |-------------------------
weight. | from | to
_______________________________________|____________|____________
| |
1. Water. 1 | +10° C. | -15.5° C.
Ammonium nitrate. 1 | |
2. Dil. hydrochloric acid. 10 | +10 | -17.8
Sodium sulphate. 16 | |
3. Dil. hydrochloric acid. 1 | +10 | -16
Sodium sulphate. 1½ | |
4. Snow. 1 | + 0 | -32.5
Sulphuric acid. 4 | |
Water. 1 | |
5. Snow. 1 | - 7 | -51
Dil. sulphuric acid. 1 | |
6. Snow. 1 | -23 | -49
Dil. nitric acid. ½ | |
7. Snow. 1 | 0 | -17.8
Sodium chloride. 1 | |
8. Snow. 1 | 0 | -49
Calcium chloride. 1.3 | |
9. Snow. 1 | 0 | -33
Hydrochloric acid. 0.625 | |
10. Snow. 1 | 0 | -24
Sodium chloride. 0.4 | |
Ammon. chloride. 0.2 | |
11. Snow. 1 | 0 | -31
Sodium chloride. 0.416 | |
Ammon. nitrate. 0.416 | |
_______________________________________|____________|____________
* * * * *