ON VEGETABLK MUCILAGES. S9 



hours'' the whole became opake. In No. 7 an immediate 

 opacity was produced, and after some time a precipitate fell 

 down. There was an immediate precipitate in No. 8 : but 

 in No. 9 there was no effect produced. If the oxysulphate 

 of iron be added to a solution containing -g- of its weight of 

 gum, the whole is immediately converted into a solid, trans- 

 parent, orange coloured jellvi; When the solution is so far 

 diluted as to contain only a" thousandth of its weight of 

 gum, alcohol no longer produces any visible effect ; while a 

 strong solution is immediately converted into a white, and 

 perfectly opake fluid. 



A substance which, in its physical properties, bears a Cherry tree 

 strong resemblance to gum arabic, is the gum which exudes fljfJrently br 

 from the cherry tree ; but I found the effects of reagents reagent*, 

 upon it to be considerably different^ When the acetate of 

 lead is added to a mucilage of cherry gum, there is no pre- 

 cipitate thrown down, but there appears a slight tendency 

 to coagulation, and in the space of 24 hours the gum ap- 

 pears to be separated from its solvent in the form of tine fila- 

 ments. The nitro-rauriate of tin converts the mucilage into 

 a solid jelly of a light yellow colour; the oxysulphate of 

 iron causes no precipitation or coagulation, but changes th-e 

 colour to a blackish brown ; the nitro-muriate of gold causes 

 an immediate opacity, and changes its colour to a light 

 brown, but there is no precipitate thrown down ; the super- 

 acetate of lead and the nitrate of mercury produce no effect. 

 When alcohol is added to a strong solution of cherry gum. Part of its so- 

 a number of filaments are formed, but the erreatest part of ^"tion incorpo- 

 ,, ., , . i. VI XT- 1 1 1 • 1 rates with alco^ 



the mucilage seems to mcorporate with the alcohol without hoi, 



undergoing any alteration ; the solid gum is not, however, 

 in the slightest degree soluble in boiling alcohol. The in- 

 fusion of galls produces no effect upon the mucilage of 

 cherry gum. The cherry gum, when first dissolved in water, Separates from 

 forms a uniform and transparent solution, but after being water by stand- 

 kept for some days in a warm atmosphere, it gradually ex- *"^* 

 hi bits a tendency to separation, a number of dark films are 

 formed in it, which rise to the surface, and the whole be- *^ 



comes slightly turbid *, 



* The result of my experiments on cherry gym will be found to differ 

 very considerably from those of Dr. Thomson. Chem. V, 48. 



Tragacanth 



