BY R. GREIG SMITH. 865 



acids, for in several of my recent papers I have shown that gums 

 such as arabin and galactan, which differ widely in their chemical 

 nature, give identical chemical reactions; furthermore, an organ- 

 ism, e.g., Bact. pararabinum, may, when grown at different 

 temperatures, produce gums that differ in these reactions. But, 

 unreliable as they are, we must utilise the reactions, because 

 they are probably as trustworthy as an}^ other chemical feature. 

 The physical properties, such as the solubility and the action 

 upon polarised light, are of no value in comparing a natural with 

 a laboratory product. Perhaps the most reliable feature of the 

 gums is the saccharine product of hydrolysis, for we expect that 

 there can be no variation in the sugar or sugars of which the 

 gum is presumably an anhydride. 



The products of hydrolysis of the natural gum were examined. 

 The gum was first of all precipitated from aqueous solution by 

 alcohol and tested for reducing sugars. None being found, the 

 gum-acids were hydrolised by being boiled with 5 % sulphuric 

 acid for eight hours, and the solution, after neutralisation with 

 barium carbonate, was tested for unaltered gum and for reducing 

 sugars. The former test was negative, the latter positive. The 

 osazones were precipitated, and after purification with ether were 

 found to have the usual crystalline appearance, i.e., stellate 

 groups of yellow needles, of the ordinary osazones. In the 

 examination of the osazone, a number of fractions were obtained. 

 These had melting points ranging from 180^ to 184° C. They 

 could not be resolved into osazones, melting above 184°, and the 

 impurities, which were soluble in ether and in cold water, gave 

 a non-crystalline deposit upon evaporation. 



The osazone was apparentl}'- simple, but its melting point did 

 not coincide with or approximate to that of any of the well- 

 known sugars excepting perhaps rhamnose. That the reducing 

 substance was a derivative of galactose was practically certain, 

 for, upon oxidation with dilute nitric acid, the gum yielded 

 mucic and oxalic acids, and during hydrolysis furfural was 

 detected. But on account of the inability to identify the gum 

 by means of the osazone as an anhydride of a known and com- 



