60
THE NATURE AND
[sect. II.
Log. 60 is - - 177815
and one sixth is - 0-29636
constant log. - 2*24797
Log. 350-2 - - 2-54433
from which subtract 100, and it gives 250°*2 for the temperature. Mr. Southern's
experiment gives 250 o, 3.
90. When sea water is employed, as it boils at a different temperature, the
force of the steam is different. The correction in the rules is easily made by find
ing the constant number which corresponds to a force of thirty inches of mercury,
at the boiling point, with different degrees of saturation with salt. Many of the
people employed about boat engines are not yet aware that there is a difference
between the temperature of steam from common water, and that from salt water,
when the force is the same. I will show in another place (Sect, iv.) the effect this
has on the power of the steam engine, but at present our object is to determine the
force of the steam. Mr. James Watt was the only person who had made experi
ments on the steam of salt water; they were made in 1774. 1 He does not give
them as being very accurate ones, but they are sufficient to establish the fact that
there is a difference ; and Mr. Faraday has lately had occasion to satisfy himself
on the same point, by various experiments. 2
91. The following table gives the boiling points of solutions of different salts
in water.
Name of salt.
Dry salt in 100
parts by weight
of the solution.
Boiling point.
Authority.
Acetate of soda
60
256°
Griffiths. 3
Nitrate of soda
60
246
Common salt
37
226
My trials.
Muriate of soda
30
224
Griffiths.
Ditto
222-35
Achard. 4
Sulphate of magnesia
57*5
222
Griffiths.
Sulphate of lime
45
220
Alum
52
220
Sulphate of iron
64
216
Sulphate of soda
31-5
213
Ditto
217-6
Achard.
1 Robison’s Mechanical Phil. vol. ii. p. 34. 2 Quarterly Journal of Science, vol. xiv. p. 440.
3 Quarterly Journal of Science, vol. xviii. p. 90. 4 Thomson’s Chemistry, vol. ii. p. 14,