Church. — On the Chemistry of Phormium tenax, 261 



principle ; ether removes oil and fat ; and so on witli other solvents. I 

 propose to describe the methods used for isolating the several proximate 

 principles of the plant under the respective headings " Gum," " Sugar," etc. 



A. — Gum. 



It is to be hoped that much of the confusion once existing as to the gum of 

 the PhormiuTTh has been cleared up in consequence of recent researches. 

 The gummy matter, which is chiefly found on the inner (or proximal) surfaces 

 of the butts of the leaves, presents no remarkable character, and I cannot 

 suggest any use for which it would be likely to prove peculiarly applicable. 

 It presents the following characters .• — When partially dried it swells in cold 

 water, and dissolves almost perfectly in hot : the solution forms, on cooling, a 

 somewhat ropy jelly. The gum has a distinct alkaline reaction to test-paper ; 

 and when burnt, leaves a white ash, which contains much potash and lime. 

 The gum is not coloured by iodine either before or after treatment with 

 sulphuric acid : this shows that it is distinct both from starch and from 

 cellulose. [A few particles of vegetable tissue often occur in the Phormium 

 gum, and these will of course be coloured by iodine if they have previously 

 been treated with sulphuric acid.] A ropy but clear solution of the gum in 

 water was rendered at first milky by the addition of two measures of alcohol ; 

 then a coagulum of white filaments separated. This was a precipitate of the 

 unchanged gum, still retaining the mineral matters (potash and lime) belonging 

 to it in the crude state. A solution of the gum is pi-ecipitated by basic lead- 

 acetate, but not by the neutral acetate. The gum is transformed very readily 

 into sugar by boiling it with dilute sulphuric acid. 



An attempt was made to purify the gum from its alkaline and earthy salts 

 by means of Graham's dialytic process. An aqueous solution of the gum was 

 acidified withdilute acetic acid, and poured into a floating dialyzer of parchment- 

 paper. A certain qiiantity of saline matter did escape in the course of forty- 

 eight hours into the water employed, but the greater part of the mineral matter 

 of the oiiginal gum remained in the solution upon the dialyzer. It should be 

 noted that gum arable may be almost completely forced from mineral matter 

 by such treatment. 



I find that a solution of the Phormium gum yields, on evaporation, a 

 residue which may be almost completely re-dissolved by boiling water. 



B, — ^Wax or Fat. 



The percentage of fixed fat or wax in the fresh plant of Phormium is not large, 

 generally averaging less than 1 per cent. Most of this fat is on the surfaces of 

 the leaf, and may be removed by the action of a caustic alkali of soap, or of a 

 solvent such as ether. It helps to impart the " bloom " to the leaf, and forms 

 a film, or fine coating, which throws off water. To the presence of this wax 



