311 



perties, bring slowly to dryness, and in tlie first place see if it 

 agrees in properties with quinic acid (page 183). 



(Ji) Free the liquid separated from the precipitate g from oxyd of 

 lead by precipitating with carbonate of ammonia, and evaporate 

 to a syrup over a water-bath, in order to drive off most of the 

 acetic acid and of the ammonia. Of acids this syrup may con- 

 tain especially lactic and quinic acids, but probably, besides, matters 

 of an alkaloidal, or of an indifferent nature (bitter substances, 

 sugai'). 



To recognise lactic acid, mix a part of the syrup with an equal 

 volume of a cold saturated solution of acetate of zinc, and allow 

 the mixture to stand in a cool place for one or two days. If no 

 crystals have formed after this period, no lactic acid is present ; 

 in the other case, a crystalline mass, usually in the form of a crust 

 and consisting of lactate of zinc, is obtained, which is further to be 

 examined regarding its amount of water of ciystallisation and of 

 oxyd of zinc (see Lactic acid, p. 116). 



Quinic acid is recognised by boiling a large quantity of the 

 syrup with milk of lime until the ammonia is driven off, and then 

 pi'oceeding as indicated under Quinic acid (p. 183). 



Should the syrup have a bitter taste, try if its aqueous solution 

 with tannic acid will produce a precipitate. (This has been tried 

 already on page 301, but with a weaker solution, and may with a 

 better prospect of success be repeated now on a more concentrated 

 solution). Should a precipitate arise in the sample by tannic acid, 

 then the whole rest of the syrup is pi-ecipitated likewise. "Wash 

 the precipitate as well as possible (p. 288), mix well with oxyd of 

 lead or with white of lead, dry in a gentle heat and extract with 

 alcohol. The tannic acid remains in combination with oxyd of 

 lead, while the respective substance passes pure into the alcohol, 

 remains after the evaporation of the solvent, and may then be 

 examined regarding its properties. 



On the contrary, if no turbidity is produced by tannic acid, 

 digest the aqueous solution of the syrup with a great quantity 

 of animal charcoal over the water-bath for several hours, collect 

 the coal on a filter, wash with cold water, transfer it moist, but 

 freed from superfluous water, into ten times the weight of the dry 

 coal employed, alcohol of 95%, heat and boil for a quarter of an hour ; 

 filter hot, wash with hot alcohol, and evaporate the united alcoholic 

 filtrates with a very gentle heat. Should an amorphous mass 

 remain without any signs of crystallisation, try if by treating with 

 ether a separation, purification, &c., can be effected. The closer 

 investigation will show whether the substance is of a basic or of 

 an indifferent nature, and it must be treated accordingly as indi- 

 cated before. 



Keep the syrup for at least a week in the cold. Anything which 

 will have separated after this period, either of a pulvenilent or of 



