SACCHARINE AND ASTRINGENT EXUDATIONS OF GREY GUM. 187 
not darkened, nor was any caramel odour perceptible, but some 
alteration had taken place, as Fehling’s solution was slightly 
reduced on heating, although the same sugar did not do so before 
it was melted ; on continuing the heating at the same temperature 
the alteration of the sugar becomes more pronounced. It appears 
therefore, that the sugar required to be heated to 100° C. to 
satisfactorily remove the whole of the water of crystallisation, 
and that it is not necessary to heat beyond that temperature. 
The different formule that have been assigned to raffinose or 
melitose by different chemists are to a certain extent partly trace- 
able to the different percentage results of the water of crystallis- 
ation obtained by them. Ritthausen found but 13-64 per cent. 
of water and judged the formula to be C,,H,,.0,, + 3 H,O, whilst 
Loiseau obtained 15 per cent., or corresponding to the formula 
C,;H;,0,, + 5 H,O which is the present one given to this sugar. 
Berthelot! found that when crystallised from dilute alcohol the 
Sugar could be obtained containing six molecules of water. 
Scheibler? has pointed out these difficulties and advises that the 
Sugar be dried partly over sulphuric acid and completely on the 
water-bath. I found no difficulty in obtaining concordant results 
when the sugar was heated in the air bath at 98 — 100° C. until 
constant, reaching that temperature by slow degrees. 
An aqueous solution of the pure sugar prepared as previously 
described, was found to be strongly dextro-rotatory and the specific 
rotation for a ten per cent. solution at a temperature of. 20° C. 
was found to be [a], + 104-25. 
The melting point of the sugar also required to be carefully 
determined. When tested in a tube closed at the end, and heated 
in a liquid, the sugar from which the water of crystallisation had 
not been removed melted at 80°C. When slowly heated in the air 
bath the water is removed at 100° C., and on slowly raising the 
temperature the sugar melts at 118° 0. (uncorrected). If the 
mercury rises too rapidly the melting point is irregular. When 
1 Compt. Rend. crx., 548. 2 Ber. loc. cit. 
