606 



Scientific Proceedings, Royal Dublin Society. 



Contraction on, mixing. 

 From the density determinations of acetone-water mixtures and n-butyl 

 alcohol-water mixtures, the percentage of contraction on mixing has been 

 calculated in the following way : — 

 Using the formula 



IF, + W, W x W, 



D 



A + A 



(in which W x and W« represent the percentage composition by weight of the 

 two components, and D, D x and D« are respectively the densities of the mixture 

 and the separate components), and neglecting contraction, the calculated 

 density was obtained. Then from the observed and calculated densities the 

 volume of one gram was calculated. The difference between the observed 

 and calculated volumes of a gram, expressed as a percentage of the latter, is 

 given as the contraction. Tables III and IX show the values so obtained, and 

 curves plotted from them are given in figs, o and 4. It will be noticed 

 that the curve of contractions for acetone-water mixtures is very regular, 

 approximating to a straight line for mixtures containing up to 30 per cent, 

 of acetone. The maximum contraction is reached when there is about 52-54 

 per cent, acetone present. The descending curve is also very regular. These 

 results agree substantially with the contractions observed by McElroy (loc. cit. ) 

 on mixing acetone witli water (allowing for the fact that he used slightly 

 denser acetone). He states that the contraction on mixing these liquids ap- 

 pears to reach its maximum when the weights of acetone and water are equal. 



Table III. Table of Densities and Contractions of Mixtures of Acetone and 



Water. 



