66 SUBSTANCES SOLÜBLE LN TV ATE B. 



allowed to stand foi' twentj^-foiir hours in a cool place in a Avell- 

 closed vessel. The precipitate is collected on a tared filter, washed 

 with 66 per cent, spirit, dried and weighed. Both filter and sub- 

 stance are then incinerated and the ash weighed, that of the filter 

 being deducted. If the precipitate itself possess the characters 

 of vegetable mucilage (§§ 195, 196) and contain not more than 

 5 per cent, of ash, it may be assumed the latter corresponds to 

 the lime and potash usually found in such mucilages. But if the 

 percentage of ash be larger, and it contain much carbonate of 

 lime or potash, attention should be paid to the possible presence 

 of salts of vegetable acids Avith these bases, such as acid tartrate 

 of lime or potash, etc. (§ 74). 



That the precipitate really contains vegetable mucilage may be 

 proved by its dissolving in water to a mucilaginous liquid Avhich 

 does not reduce Fehling's solution until after it has been boiled 

 for some time with dilute hydrochloric acid. Its concentrated 

 solution is precipitated by basic acetate of lead. It is also 

 occasionally precipitated by ferric chloride and thickened by 

 solution of borax or soluble silicate of soda. See also §§ 193 to 

 196. 



§ 74. Vegetahle Alhunen. — Incomplete solubility of the mucilage 

 precipitate would indicate the presence of allnimen, but, by the 

 method of examination adopted, the quantity Avill usually l)e so 

 small that it may be neglected. (See also §§ 92 d seq.; 95 et seq.) 

 If, hoAvever, Lassaigne's test show that the precipitate contains 

 much nitrogen, the results of the estimation, of legumin and 

 albumen, which will be subsequently made, must be deducted 

 from the Aveight of mucilage, etc. If, on treating the mucilage 

 precipitate Avith a little Avater, a difficultly soluble crystalline sub- 

 stance be observed, examination should be made for tartrate of 

 lime or acid tartrate of jiotash, Avhich, if present, should be 

 estimated by precipitating with neutral acetate of lead and should 

 be deducted from the weight of the mucilage. 



J^ 75. Initlin. — If subterranean parts* of plants belonging to 

 Compositae or allied orders are under examination, they may, 

 even though previously dried, yield a little inulin to Avater. 

 After precipitation Avith alcoliol it is not rcdissolved by Avater at 

 the ordinary tenq)erature, but is freely soluldo Avlicn Avarmed 

 to 56°. It is kcA'O-rotatory, is converted l)y treatment Avitli dilute 

 acid into levuloi-e, and may Ije [estimated by determining the 



