BY R. GREIG SMITH. 593 



gum, unaltered saccharose, and a reducing sugar or mixture of 

 sugars. A small quantity of acid was also formed. In esti- 

 mating the sugars, it is necessar}^ to remove the gum, and to do 

 this various precii^itants or coagulants were tried. Basic acetate 

 of lead was found to be useless, as a diffuse emulsion was formed 

 which refused to coagulate. The addition of milk of lime to the lead 

 emulsion produced coagulation, but an equally good coagulation 

 was obtained by the use of milk of lime alone. Lime is not an 

 ideal coagulant on account of the possible formation of difficultly 

 soluble compounds with the sugars, especially with levulose. 

 The percentages of saccharose inverted and not inverted might 

 not, therefore, be a true index of the rate of change when lime 

 is employed, and a number of analyses bore out this contention. 

 A coagulation of the gum was also attempted with anhydrous 

 magnesium sulphate and with calcined magnesia, but these 

 magnesium compounds were found to be quite inert — no coagu- 

 lation was obtained, and the filtrate appeared similar to the 

 solution before the addition. Acid mercuric nitrate, like basic 

 lead acetate, formed a diffuse emulsion which passed slowly and 

 without retention through filter paper. The neutralisation of the 

 acid with sodium hydrate, until die emulsion became yellowish, 

 was also without effect. 



The only safe coagulant appears to be alcohol, and in the 

 following work upon the action of the bacillus this was used. 

 After many trials the following method was adopted. Twenty 

 c.c. of the culture is slowly dropped into 60 c.c. of strong alcohol 

 (methylated spirit distilling at 77*5 - 78-5° C.) while the latter is 

 being vigorously stirred. A drop of phenolphthalein solution is 

 next added, and the acidity neutralised with dilute sodium 

 hydrate. Finally 20 to 40 c.c. of alcohol are added to make 

 certain that coagulation has been complete. After standing for 

 two or three hours, the gum is filtered off upon a dry and tared 

 filter and scraped from the beaker, to which it adheres somewhat 

 firmly. If necessary, the adhering particles are treated with a 

 small quantity of hot water, the gum precipitated with excess 

 of alcohol and filtered. The gum is dried at 100° C. until of 



