ROSACES 397
The Nabonnand roses are to-day members of the " Roses des jardins",
or mixed garden roses, used for distillation purposes. These roses, dis-
tilled by themselves, yield an otto having a specific gravity 0*8537 at 30°,
rotation - 2- 2°, melting-point 19°, and ester number 42. As judged by
the usual standards set up by limited experience, this otto would be con-
demned by non-experts on account of its extraordinarily high ester-
content.
The Van Houtte roses, too, have a quite different character from any
other, in so far as they yield an otto with the very high optical ro
t
ation
— 11°, and the Brunner rose yields an otto which melts at 28°, rarely
below this.
The writer has examined authentic otto distilled from the Rose d'Hai
during 1916, and found it to melt at 8° and to have a specific gravity of
about 0-880. Its alcohol value was 90 per cent., consisting almost entirely
•of; geraniol.