Lyons — Volume Change on Fusion. 67 



Reduction of Observatiom to defennine at any Temperature T° C. the 

 Volume (V) of one (jramme of the substance. 



We have the following data : — 



Mass of mercury filling one centimetre of stem = a 



Density of mercury at any temperature from tables = p 



Mass of mercury in apparatus in the preliminary experiment = /!/„ 

 Keading of meniscus at any temperature T°C. in this 



preliminary experiment = i2„ 



Mass of mercury in tlie apparatus previous to introducing 



substance = M 



Reading of meniscus corresponding to M at the known 



temperature of cold water ^ 0. = b 



Mass of mercury expelled on introducing substance = m 



Weight of substance in bulb during test = W 



Reading of meniscus at any temperature T°C. when tlie 



substance was in the bulb = R 



The reading R^ showing the expansion of mereiu'y in glass in the 

 preliminary exjjeriment is plotted against tlie temperature. A straight- 

 line graph is obtained from which the value of R„ at any temperature may 

 be found. The coefficient of apparent expansion of the mercury and the 

 coefBoient {g) of real expansion of the glass may also be found in the 

 usual way. 



The mass of mercury M, previous to introducing substance, filled the bulb 

 and stem to the mark b at the temperature t° C. Let the reading R^ corre- 

 sponding to the mass of mercury M^ in the original bulb be equal to a at f^G. 

 The change in volume {vt) of the bulb at f C. due to altering the capillary 

 above it will be 



M^+{b-a)a-M ' 



Pt 

 At any other temperature T° C. this alteration in the volume of the bulb is 



V^=Vt{l + g{T-t)\. 



As already pointed out, it is possible to arrange to liave the bulb 

 alteration v so small as to be negligible. It is in all cases very small, and 

 the variation with temperature of the corresponding mass of mercury v ><■ p, or 



v^. Pj,- Vt . pt, 

 is of a very small order. 



At any temperature T° C. the substance ( JF) in bulb and amass of mercury 



