17 
If the face p is adjusted 
in the stauroscope with the sides 
a a the cross stands normal 5 a 
proof that the crystalisation is 
not triclinic. 
The measurements could 
only be made by the reflection 
of candle light with the use 
of the lens. 
MELTING AND BOILING POINTS. 
The melting point is 46 0 C., but the temperature 
at which this substance solidifies again is much lower 
viz. 36 0 C., making a difference of ten degrees between 
the melting and freezing points. These observations were 
carefully made by exprimenting on several different 
portions of the resin. 
This somewhat strange behaviour has already been 
observed in other bodies e. g. Oleaic acid when melted 
does not solidify till cooled to 4 0 C.; its melting point 
is 14 0 C.: Doeglinic acid which melts at 16 0 C. congeals 
a few degrees above 0 °C. 
To determine the boiling point of this substance 
about five grams were put into a small retort holding 
a thermometer running up to 320 0 C. The latter was 
lowered almost to the surface of the melted resin, and 
the heat gradually increased till the mercury reached 
310°, when the thermometer was taken out, and the 
retort more strongly heated. Soon oil drops began to 
2 
