Chemistry and Physics. 233 



used, consisting of two bulbs, one to contain pure carbon disulphide, 

 the other to hold the solution; these vessels being provided with 

 mercury traps by which they could be isolated from each other 

 and from the pumps. The vapor pressure of the pure carbon 

 disulphide was first determined, then that of the solution ; the 

 ratios of the differences of the two pressures to the vapor-pres- 

 sure of carbon disulphide at the corresponding temperatures 

 being proportional therefore to the number of dissolved mole- 

 cules per unit of solution. The experiments with sulphur were 

 conducted between 0° and 13 - 8° and show that for solutions up to 

 20 per cent, the molecular depression corresponds to a sulphur 

 molecule containing 8 atoms for the more dilute, and containing 9 

 atoms for the less dilute, solutions. For phosphorus the vapor- 

 pressures were measured at 0°, several solutions being employed. 

 The molecular depressions observed corresponded approximately 

 to a tetratomic molecule, in the case of a 3 per cent solution ; in- 

 creasing somewhat as the solution was made stronger. — Real. 

 Accacl. Lincei, ii, 210, 1892; J. Chem. Soc, lxiv, ii, 511, Nov. 

 1893. G. F. B. 



4. On the Influence of Heat on Chemical Reactions. — An 

 elaborate investigation has just been made by Lemoine upon the 

 influence of heat, unaffected by that of light, on the reactions 

 which take place in aqueous solutions containing ferric chloride 

 and oxalic acid. When these substances are present in equiva- 

 lent proportions, the interaction is irreversible and proceeds 

 according to the equation 



(FeCl 3 ) 2 + H 2 C 2 4 =(FeCl) 2 + (HCl) 2 +(C0 2 ) a 



The rate at which decomposition takes place at any temperature 

 is found to follow the well known law of mass action, which 

 states that the amount of substance which is being decomposed 

 at any instant is proportioned to the amount of unchanged sub- 

 stance contained in unit volume of the solution. The concentra- 

 tion remaining the same, the rate of change is found to vary 

 markedly with variation in temperature. For example, while 

 0*16 of the original amount of substance was decomposed at 100°, 

 in one hour, it was found that at ordinary temperatures only 0*019 

 equivalent had reacted after six years. Water accelerates the 

 speed of change according to a law which varies slightly with 

 the temperature. A slight excess of oxalic acid also accelerates 

 it, but a large excess either of oxalic acid or of ferric chloride 

 retards it; while an excess of concentrated hydrochloric almost 

 completely arrests it. The author has studied both chemically 

 and thermochemically the effects whrch these and other foreign 

 substances have upon the course of the simple reaction and finds 

 that they may be explained by the production of secondary reac- 

 tions. — Ann. Chim. Rhys., VI, xxx, 289, Nov. 1893. G. F b. 



5. Motochemistry or Stereochemistry. — The term " motochem- 

 istry" has been proposed by Molinari to indicate the view that 

 the constitution of compounds depends on the intramolecular 



