THEORY OF CONCENTRATED SOLUTIONS. 147 



The agreement in this case is much better than is likely to 

 be obtained as a general rule. 



It shows that in any ease this geometrical method of evaluat- 

 ing .r and K gives at least approximately correct results. 



Summary. 



The main results of the present research are as follows:— 



1. Taking an ideal mixture as one which obeys the mixture 

 law, then the property-composition curve itself can in general 

 afford very little evidence of the formation of a compound 

 between the two components of the mixture. The curve 

 obtained by plotting the deviations from the straight line against 

 the composition of the mixture is, however, of considerable 

 importance. 



2. The deviation from the straight line is proportional to 

 the amount of compound formed. 



3. The active mass of the compound is a maximum when 

 the mixture as a whole has the same composition as the com 

 pound formed. 



4. It is possible to determine the formula and the degree of 

 dissociation of a compound formed in a liquid system from a 

 consideration of physical data alone. 



5. Although temperature changes may affect the form of 

 the property-composition curve, especially as regards the position 

 of a maximum therein, the position of maximum deviation from 

 the straight line is independent of temperature change. 



6. The principles stated above have been applied in the 

 investigation of the equilibrium 



K 2 SO; -i- H.S0 4 = = aKHS0 4 



in aqueous solution. 



A New Vegetable Oil. — In No. 134 of the Journal 

 d' Agriculture Tropicale, pp. 233-234, C. de Mello Geraldes 

 describes an oil from Mozambique, obtained from the fruit of 

 Trachylobium, sp., which contains an average of 12.48%. From 

 its chemical and physical constants, and the fact of its being 

 half drying, it may be grouped with cotton seed oil. It seems 

 suitable for soap manufacture, and is valued at 3d. per lb. 



