92 



Messrs. V. H. Veley and J. J. Man ley. 



determined by five different thermometers, namely, the one used for 

 the investigation, one standard by Baudin graduated to 0'02 C., one 

 by Delaunay, and two by Becker, these last three graduated to O'l C. 

 All these instruments were calibrated in our previous investigation, 

 and have subsequently been submitted again to the same process with 

 the same results. 



In each case two independent determinations of the water and acid 

 contents were made, so that either four or two results were obtained 

 according as all the determinations or one in each pair were different. 

 The following results were obtained for the density at 24'2/4 : 



The mean of all the above determinations is 1-26733, with a probable 

 error of 0-00002 calculated from the ordinary formula 



0-674 



though it would appear probable from the results that the thermo- 

 meters I, II, and V gave identical readings, but different from III and 

 IV ; this difference is probably equal to about 0'02 C. However this 

 may be, the errors accumulated by the variations of one instrument 

 would not affect any conclusions, and the method, as regards tempera- 

 ture, gives accurate results. 



A number of duplicate experiments were made in which one or more 

 of the following were varied : (i) stock acid ; (ii) pyknometer ; and 

 (iii) standard alkali ; the difference in the values obtained did not 

 exceed one or two units in the fourth place of decimals, which would 

 cause no appreciable error in the contractions. 



Further, it is most probable that the divergence in values obtained 

 for the contractions of acidic and saline solutions, to which attention 

 has recently been drawn,* arises rather from errors of analysis and 

 unequal amounts of impurities in materials, than from density deter- 

 minations with all their consequent errors. 



* Wade, ' Journ. Chem. Soc.,' 1899 (Trans.), p. 254. 



