Physics and Chemistry. 219 



ences of level in this tube and in a manometer gauge connected 

 with it, the vapor pressure was calculated. The temperatures 

 chosen were the boiling point of methyl salicylate under atmos- 

 pheric pressure; of bromonaphthalene under a pressure of 

 612 - 8 mm ; of the same under a pressure of 756*2 mm ; of mercury 

 and of sulphur. The temperatures corresponding were 222-15°, 

 270-35°, 280*6°, 358-47° and 448°. The vapor pressures observed 

 were 34-4, 124-35, 157-15, 767'43, 2904-5 millimeters. The 

 authors having shown that if a diagram be constructed in which 

 the ratios at the same pressure between the heats of vaporization 

 of two liquids at various pressures the same for both, form the 

 abscissas, and the absolute temperatures of one of the two liquids 

 corresponding to these vapor pressures, form the ordinates, then 

 the points representing the relations between these ratios and 

 the absolute temperatures will lie in a straight line — constructed 

 the curve from the above data, combined with the absolute tem- 

 perature of water required to give the above vapor pressures, and 

 found it to be a straight line. By its means, other desired values 

 were interpolated and a complete table of vapor pressures 

 obtained for mercury and water between 135° and 520°. A 

 second table is also given, in which the vapor-pressures are calcu- 

 lated for each degree centigrade ; enabling the temperature of 

 mercury vapor when used in a jacket, to be ascertained from the 

 observed pressure. — J. Chem. Soc, xlix, 37, Jan., 1886. G. f. b. 



4. On the limits of the conversion of Sodium carbonate into 

 Sodium hydrate by means of Lime. — Lunge and Schmid have 

 investigated the conditions of concentration, temperature and 

 pressure under which the maximum conversion of sodium car- 

 bonate is effected by means of caustic lime. Solutions of pure 

 sodium carbonate of different degrees of concentration were 

 heated to boiling for an hour in an iron vessel with an excess of 

 lime, at the ordinary atmospheric pressure. Other similar solu- 

 tions were similarly treated in copper tubes for the same time r 

 continual agitation being secured by means of a stone placed 

 inside. After the operation the solutions were analyzed ; the 

 total alkalimetric titer being effected with methyl orange as an 

 indicator, and the sodium hydrate determined by Winkler's 

 methoa (addition of barium chloride and phenol-phthalein and 

 titering with oxalic acid till the color disappears). As a result^ 

 it appears that at ordinary pressures, for solutions containing 2, 

 5, 10, 12, 14, 16 and 20 per cent of carbonate, 994, 99-1, 97*3, 

 96-5, 95-0, 93-8, and 90*9 per cent respectively of the sodium had 

 been converted into hydrate by this treatment. At high pres- 

 sures, and at temperatures varying from 148° to 153°, for solu- 

 tions of 10, 12, 14, 16 and 20 per cent of carbonate, 97*3, 96 6, 

 96 - l, 95-1 and 91 -6 per cent of the sodium was in the condition of 

 hydrate. These figures show that there is no special advantage 

 in heating under high pressure ; a fact confirmed on the large 

 scale by Jurisch who heated a mixture of specific gravity 1-157 

 to 1-177 for six hours under a pressure of three atmospheres and 



