Occasional Notes. 151 
yielded by alcohol, however, being by far the larger. They consist of 
short needles and plates with square ends, evidently belonging to the 
trimetric system. As already mentioned laurite resembles mannite in 
crystalline form but is quite unlike dulcite which crystallises in mono- 
clinic prisms with octohedral summits. Laurite exhibits the same 
general properties which characterise dulcite and mannite. It melts 
and partially sublimes when heated in a tube, dissolves in sulphuric 
acid without blackening and is not altered by caustic alkali solution. 
It is freely soluble in water, sparingly soluble in strong spirit, insoluble 
in ether and chloroform. It forms a blue solution with a mixture of 
copper sulphate and potash, but does not reduce it on boiling. It pre- 
cipitates neither normal nor basic acetate of lead, but forms a bulky 
white precipitate with ammoniacal acetate of lead. The crystals slightly 
polarize light but, probably in consequence of the smallness of the 
crystals, not nearly so powerfully as either mannite or dulcite. Laurite 
is slightly sweet in taste and to a degree about equal to dulcite. The 
ultimate analysis of laurite gave numbers fairly agreeing with the 
formula C6 Hu Laurite dissolves with effervescence in heated dilute 
nitric acid but does not form mucic acid like dulcite. Saccharine acid 
is probably produced however. Laurite is very non-hygroscopic and 
bears a considerable degree of heat without being sensibly altered. It 
did not lose weight in the hot air bath very appreciably until the tem- 
perature rose above 210 degs. c. Heated in a narrow tube in a paraffin 
bath no particular decomposition was observable until the temperature 
reached 280—290 degs. c, when darkening and evolution of gas set in. 
Laurite melts when heated. Its melting point and that of both mannite 
and dulcite were carefully determined. Preliminary experiments had 
shown that the rnelting point of laurite was much higher than that of 
mannite but closely approached, if it was not identical with that of 
dulcite. But the melting points of both dulcite and mannite recorded 
by different observers varied so much that their careful redetermination 
became necessary. 
The following are the corrected melting points of three specimens of 
mannite, five of laurite and two of dulcite : — 
Mannite 166-62 degs., 166-65 degs., 166*67 degs., 166-58 degs., 166-52 
degs., 166-56 degs. 
Mean melting point = 166-60 degs. c. 
Laurite 186-64 degs., 186-72degs., 18687 degs., 186-60 degs , 186-63 degs. 
