and its bearing on the Nature of Solutions. 491 



(1) Is the molecular depression — using this term to mean 

 the lowering of the freezing-point produced by one foreign 

 molecule on 100 molecules (not parts by weight) of the solvent 

 — a constant, whatever the foreign substance is, provided 

 that the amount of the latter is not greater than that which 

 would give a pressure equal to that produced by it in the 

 gaseous state at the same temperature ? 



(2) Are such deviations from regularity, as are observed 

 in exceptional cases, in the direction in which they should be 

 according to the theory ? 



(3) Ts the depression a constant whatever the solvent is ? 



(4) Is the depression constant when the proportions of 

 the solvent and dissolved substance are varied within the 

 limits mentioned in (1) ? 



(5) When stronger solutions are taken, is the deviation 

 from regularity in the direction in which it should be 

 according to the theory ? 



(6) Is the deviation always in the same direction, and 

 always regular ? 



I believe that I can show that the answer to every one of 

 these questions is an unqualified No. 



The main facts of the case as elucidated by Raoulf s work 

 are that, when various substances are dissolved in 



Benzene, 

 Nitrobenzene, 

 Ethylene dibromide, 

 Formic acid, 

 or Acetic acid, 



the molecular depression is about o, 63, though there are a 

 few substances in each case which give an abnormal depres- 

 sion of about half this amount. 



With water the molecular depression is generally 2 o, 06, 

 but in many cases approximates to 2°*61, values which 

 Kaoult takes to be three and four times o, 63 (1°'89 and 

 2°*52) respectively. Abnormally low values are in the same 

 proportion to the normal ones as with other solvents ; they 

 are about l o, 03 (half of 2°*06), and are obtained with some 

 inorganic substances, and with the majority of organic sub- 

 stances at present investigated. 



All these determinations apply to solutions containing about 

 1 molecule to 100 molecules of the solvent, and are, therefore, 

 three or four times stronger than they should be in order to 

 be comparable with gases under ordinary conditions. We 

 shall have to decide whether the discrepancies which they 



