On the Construction of a new Calorimeter. 463 
Then if Q denote the quantity of heat, expressed numerically, 
which radiates from a unit of surface (a square foot) in a unit of 
time (one minute), we have the following results for the substances 
specified :— 
Glass. 
9-566 a%(at'—1)+°03720 (5) 
Dry Chalk. 
Q= 8:613 a%(a'—1)+-03720 (5) ° 
Dry New Red Sandstone. 
= 8:377 a%(a'—1)+-03720 (4) prs 
Q 
Sandstone (building stone) 
Q= 8-882 a%(at—1)++03720 (4) 
45 
fe 
Polished Limestone. 
45 
Q= 9:106 a%(aé'—1)+°03720 (4) gi298 
Unpolished Limestone (same block as the last). 
"45 
@=—12:808 a9(at—1)+-03720 (4) 2233 
‘On Isoprene and Caoutchine.” By C. Greville Williams, Esq. 
This paper contains the results of the investigation of the two prin- 
cipal hydrocarbons produced by destructive distillation of caout- 
chouc and gutta percha. 
Isoprene. 
This substance is an exceedingly volatile hydrocarbon, boiling 
between 37° and 38° C.; after repeated cohobations over sodium, it 
was distilled and analysed. The numbers obtained as the mean of 
five analyses were as follows :— 
Experiment. Calculation. 
oe a 
Carbon % 1)..; «8870 Ces 160 88-2 
Hydrogen. . 12°1 eats 11°8 
68 100:0 
Three of the specimens were from caoutchouc and two from gutta 
percha. + The vapour-density was found to be at 58° C. 2°40. Theory 
requires, for C** H®=4 volumes, 2°35. The density of the liquid 
was 0°6823 at 20°C. 
Action of Atmospheric Oxygen upon Isoprene. 
Isoprene, exposed to the air for some months, thickens and acquires 
powerful bleaching properties owing to the absorption of ozone. On 
