454 Transactions. — Chemistry and Physics. 



complete solution a double determination of the temperature 

 of solidification is made, and this process is repeated six or 

 seven times if the solubility permits it. When the dissolved 

 substance is only slightly soluble it is introduced in smaller 

 quantities, and consequently in such cases the accuracy 

 cannot be so great. 



Besides the error of temperature-determination, which 

 does not exceed 1 per cent., there are several others of more 

 or less moment, Phenol is slightly hygroscopic ; but, as 

 in all cases the conditions are practically the same, this 

 source of error, which at the most is only slight, can hardly 

 influence the results. Perhaps the most serious error is that 

 caused by the non-homogeneity of the solution which is being 

 experimented with. Thus, the solute, especially if a liquid, 

 may stay on the thermometer in small quantities above the 

 solution ; the solvent also has a tendency to climb up the 

 stirrer and thermometer and sublime to the upper parts of the 

 apparatus. The errors in weighing can be entirely neglected. 

 But in a series of determinations these errors tend to disappear 

 or neutralise one another, and for this reason the rate of asso- 

 ciation is a more accurate result than the initial molecular 

 depression. Moreover, traces of impurity will, of course, affect 

 the latter, but seem to have little influence on the former. 

 Nevertheless, every effort was made to obtain the material as 

 pure as possible, and different samples were employed where 

 conveniently possible. As an example of the accuracy ob- 

 tainable in the work I may cite the ease of lauric acid. 

 Three determinations gave the following numbers for the rate 

 of association (depression 5°) : 58 per cent., 62 per cent., 

 60 per cent, (different sample of phenol). 



Most of the fatty acids employed in the investigation 

 were from Merck ; acetic acid was frozen several times, and 

 the lower members were fractionated before use. Normal 

 valeric and methylethyl acetic acids were synthesised from 

 ethyl malonate ; but, owing to the small quantities at my 

 disposal, their purity cannot be so fully guaranteed. Lauric 

 and stearic acids showed their purity by their melting-points. 

 A number of the other acids were also from Merck. Professor 

 Easterfield kindly placed his own private stock of prepara- 

 tions at my disposal. Among others I prepared the following 

 acids : brornacetic, cinnamic, ethylmalonic, brombutyric, oxy- 

 diphenylacetic, nitrosovaleric, dibrommethylsuccinic, anilido- 

 acetic, toluidoacetic, phenylanilidoacetic, amidoacetic, acet- 

 amidoacetic, mesaconic, adipic., and phenoxyacetic, all of 

 which were used in the investigation. 



In order to show clearly the method of calculating the 

 results I will give one example in full ; in the other cases the 

 final results alone are tabulated. 



