BY R. GREIG SMITH. 147 



mucin and the gums, is rendered more viscous by the presence 

 of albuminoids. Alcohol, barium hydrate, and the basic lead 

 acetates coagulate it, while neutral lead acetate and tannin have 

 no action. It is oxidised by dilute nitric acid to mucic acid. 

 When boiled with dilute alkalis it is converted into pectic acid, 

 which is insoluble in water, and which when boiled with dilute 

 acids is converted to arabic acid, that is arabin. The arabic acid 

 thus obtained is hydrolysed to pectinose (arabinose) and a little 

 known organic acid [possibly one of O'Sullivan's galactan-geddic 

 acids]. 



Had the Hakea gum been pectin, the digestion in the autoclave 

 ought to have changed part of it at least into parapectin or 

 metapectin, which are precipitated with neutral lead acetate and 

 barium chloride respectively. As these reagents did not induce 

 precipitation, the gum is probably not pectin. In view of the 

 doubtful nature of the gum, I resolved to boil it first with dilute 

 alkali, then with dilute acid, and to test the products to see if 

 any information could be gained respecting its possible affinities 

 with pectin. Accordingly pieces of gum were boiled under an 

 aerial condenser with 1 % sodium hydrate for two hours. It did 

 not appear to dissolve, but remained as slightly swollen opalescent 

 lumps in the boiling alkali. The solution was filtered oif and 

 treated with alcohol, when a small precipitate settled out. When 

 treated with water and made faintly acid, this gave a ropy solu- 

 tion like the gum before treatment. Its reactions were identical 

 with those given by the gum, so that the alkali had not altered 

 this portion. The swollen gum, after being washed with water, 

 was boiled with 1 % hydrochloric acid, in which it speedily dis- 

 solved. After an hour's boiling, the solution was neutralised and 

 treated with alcohol, when a precipitate, which became fiocculated 

 with a drop of hydrochloric acid, was obtained. The alcoholic 

 solution contained substances that reduced Fehling's solution. 

 The precipitate, thrown down by the alcohol, dissolved readily in 

 water, forming a comparatively slightly viscous solution like 

 arabin. When the solution was made faintly acid and tested, 

 coagula were obtained with ferric chloride and basic lead acetate. 



