394 BACTERIAL ORIGIN OF GUMS OF ARABIN GROUP, 



The residual gum acids which did not hydrolyse by the 2 % 

 acid treatment were dissolved in 25 c.c. of 5 % sulphuric acid and 

 warmed to expel the traces of alcohol. The solution was then 

 made up to 25 c.c. with water and boiled under a reflux condenser, 

 at first gently and then vigorously after the foaming had ceased. 

 The boiling was continued for five hours. After cooling, the acid 

 solution was treated with alcohol and a very small quantity of 

 unaltered gum removed. The alcoholic solution was treated as 

 has been already described, and the final solution reserved for 

 the preparation of the osazone. 



The solution supposed to contain arabinose was tested with 

 Fehling's solution, when a strong reduction was obtained. One- 

 half of the solution was set aside in case of accidents. The other 

 half was heated on the water bath and to it were added 2 c.c. of 

 a solution containing 40 c.c. phenylhydrazine, 40 c c. glacial 

 acetic acid and 20 c.c. water. The heating was continued for an 

 hour and the solution was cooled. The precipitated osazone was 

 filtered off, dried on porcelain, transferred to a small filter and 

 extracted with ether* to remove a black, tarry substance which 

 melted at about 98°. This was always found in the osazones 

 from the bacterial as well as the natural gums. It was never 

 obtained in working with pure sugars such as dextrose. The 

 precipitate was dried at 100° and the melting point determined. 

 This was 160°, which, together w^ith the appearance of the crystals, 

 showed it to be the osazone of arabinose. 



The solution, which presumably contained galactose, reduced 

 Fehling's solution. One-half was treated with phenylhj^drazine- 

 acetic acid and the osazone extracted with ether. The dry osazone 

 melted at 182-183°, which show^ed it to be a mixture. The 

 mixed osazone was boiled with 10 c.c. of waterf and filtered 

 through a hot filter which had been moistened with boiling water. 



"•' A preliminary moistening with alcohol is sometimes advantageous. 

 t In some cases the osazones could not be separated by water alone, but 

 by dissolving everything in dilute alcohol and slowly boiling off the alcohol, 

 the galactosazone precipitated out from the hot solution and was separated 

 by filtering through a hot, wetted filter. 



I 



