303 



If sugar has been detected by tlie reduction of copper, the 

 properties and constitution of the other product obtained by the 

 breaking up of the glucosid have to be investigated. For this 

 pui-pose decompose the greater portion of the remaining glucosid 

 by means of digesting with dilute sulphuric acid, collect what has 

 separated in a filter, wash and dry. Should, on the contrary, 

 the product be soluble in water, the acid liquid is saturated with 

 carbonate of soda and evaporated to dryness. Extract the dry 

 mass with alcohol of 95%, filter ofi" the sulphate of soda and 

 let evaporate. The product of decomposition of the glucosid will 

 separate slowly either in crystals or in a pulverulent or any other 

 form, while the sugar remains in the mother-ley. Should the 

 product be so soluble in alcohol as not to be separable from the 

 sugar by crystallising, it may be obtained by any of the three 

 following methods: — (1) If it be insoluble in pure water, evaporate 

 the alcoholic tincture and remove the sugar by means of water. 

 (2) If it be soluble in pure water, add a little yeast, destroy the 

 sugar by fermentation, filter ofi" the yeast, and evaporate. (3) If it 

 be soluble in ether, shake the dry mass obtained on evaporating 

 the alcoholic solution with ether, and evaporate the solvent. 



It may also happen that by treating with dilute sulphuric acid 

 another decomposition takes place with the glucosid (as, for 

 instance, salicin breaks up first into saligenin, and this again 

 becomes decomposed instantly into salii-etin). In order to ascertain 

 this, the substance has to be svibmitted to the action of milder 

 reducing agents, as, for instance, yeast, synaptase (purified emulsin), 

 and the jDroduct, if there be one, is compared with the one obtained 

 by means of dilute sulphviric acid. The method adopted for this 

 purpose may be the same as indicated for the production of sali- 

 genin from salicin, viz., by digesting the substance with one-tenth 

 synaptase and with water sufiicient for a solution for about twelve 

 houi's, and at a temperature not exceeding 40°, by shaking with 

 ether and by evaporating the latter. But, should the product be 

 insoluble in ether, chloroform, benzol, or any other liquid must be 

 tried which does not dissolve sugar, and therefore alcohol must be 

 left out of consideration. 



(c) The s^ihstance is non-nitrogenised, aiul is an acid. It belongs 

 to this category, if it has not only an acid reaction, but also an acid 

 taste — the least frequent of the three cases a, b, c. Should the 

 acid prove quite new or imperfectly investigated, its properties and 

 composition have to be ascertained first. Afterwards saturate the 

 acid with potash, soda, or ammonia, and test the solutions thus 

 obtained with salts of the earthy and of the heavy metals; or if the 

 latter yield no pi-ecipitates (by forming soluble compounds with 

 the acid in question) transfer the acid to these other basic bodies, 

 and investigate carefully the salts hereby produced. 



(d) The mother-leys of a or b or c, together with the liquids 



