66 SUBSTANCES SOLUBLE IN WATER. 



allowed to stand for twenty-four hours in a cool place in a well- 

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

 with 66 per cent, spirit, dried and weighed. Bpth 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 with 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 which 

 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. Vegetable Albumen. Incomplete solubility of the mucilage 

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

 method of examination adopted, the quantity will usually be so 

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

 If, however, 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 weight of mucilage, etc. If, on treating the mucilage 

 precipitate with a little water, a difficultly soluble crystalline sub- 

 stance be observed, examination should be made for tartrate of 

 lime or acid tartrate of potash, which, if present, should be 

 estimated by precipitating with neutral acetate of lead and should 

 be deducted from the weight of the mucilage. 



75. Inulin. 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 water. 

 After precipitation with alcohol it is not redissolved by water at 

 the ordinary temperature, but is freely soluble when warmed 

 to 56. It is laevo-rotatory, is'converted by treatment with dilute 

 acid into levulose, and may be^estimated by determining the 



