Chapter II., Note 27), Ramsay and Young observed that the ratio of

the absolute temperatures (_t_ + 273) corresponding with equal tension _varies_ for every pair of substances in rectilinear proportion in dependence upon _t_, and, therefore, for the above pressure _p_, Ramsay and Young determined the ratio of _t_ + 273 for water and bromine, and found that the straight lines expressing these ratios for liquid and solid bromine intersect also at 7°·05; thus, for example, for solid bromine--

_p_ = 20 25 30 35 40 45 273 + _t_ = 256·4 259 261 263 264·6 266 273 + _t_´ = 295·3 299 302·1 304·8 307·2 309·3 _c_ = 1·152 1·154 1·157 1·159 1·161 1·163

where _t_´ indicates the temperature of water corresponding with a vapour tension _p_, and where _c_ is the ratio of 273 + _t_´ to 273 + _t_. The magnitude of _c_ is evidently expressed with great accuracy by the straight line _c_ = 1·1703 + 0·0011_t_. In exactly the same way we find the ratio for liquid bromine and water to be _c__{1} = 1·1585 + 0·00057t. The intersection of these straight lines in fact corresponds with -7°·06, which again confirms the melting point given above for bromine. In this manner it is possible with the existing store of data to accurately establish and _verify_ the melting point of substances. Ramsay and Young established the thermal constants of iodine by exactly the same method.

[60] The observations made by Paterno and Nasini (by Raoult's method,