150 TlMEHRI 
manna, and of dulcite, a rare sugar occurring in plants of the order 
ScropTiitlariaceoe. Laurite closely resembles dulcite in taste, solubility, 
melting point and specific gravity, but is essentially different from it 
in the shape and system of its crystallisation and in not yielding mucic 
acid on being heated with dilute nitric acid. On the other hand, in crys- 
talline form the substance is like mannite, but greatly differs from it, 
nevertheless, in its degree of sweetness, higher melting point, inferior 
solubility in alcohol and dissimilar behaviour under the action of 
hydriodic acid. Laurite occurs in all parts of the avocado-pear tree, 
but is yielded most easily by the bark. To obtain it, the bark is broken 
into small pieces or coarsely ground and boiled with water. The decoc- 
tion is strained and precipitated with acetate of lead, filtered, and the 
excess of lead in the filtrate removed with sulphuretted hydrogen or 
sulphurous acid, again filtered, and the filtrate boiled down to a syrup, 
when it sets to a semi-solid mass of minute crystals on standing for 
some hours. It is then transferred to a beaker and boiled with methylated 
spirit, which dissolves very little of the laurite but removes glucose and 
colouring matter. The solid residue, consisting of impure laurite, is col- 
lected on a filter, pressed and recrystallised several times from water, or 
better from spirit of 40 over proof. Finally, the laurite may be pre- 
pared in a high state of purity by being recrystallized in small quanti- 
ties from rectified spirit. It is thus obtained in the form of small 
transparent needles that often form stars and, when collected and dried, 
resemble sulphate of quinine in bulk and lightness, and are quite 
different from the lustrous crystalline grains of dulcite similarly obtained. 
Laurite also crystallises from alcohol in a very different manner from 
mannite ; a saturated solution of mannite in boiling alcohol becomes 
on cooling a pulpy mass of long fibrous crystals, and the vessel con- 
taining it may be inverted without any of the alcohol flowing out, 
whereas a saturated solution of laurite in boiling alcohol deposits only 
a slight flocculent layer of short needles, and nearly all the alcohol can 
be readily decanted. 
When laurite is crystallised from water it is deposited as a white 
powder, the crystalline nature of which is only apparent under the 
microscope. In this respect therefore it exhibits a marked difference 
from both mannite and dulcite, each of which readily yields crystals of 
considerable size from the aqueous solution. The crystals of laurite 
have the same shape whether obtained from alcohol or water, those 
