319 



(a) Saturate the acid exti'act, mixed with the water used for 

 washing, with ammonia in excess. Generally only a darker colour 

 is produced ; should a turbidness be obtained, try, with a small 

 quantity, if it becomes clear again by immediately over-saturating 

 with acetic acid.* If this is not the case, oxalate of lime is pre- 

 sent. Allow the liquid to become perfectly clear — sometimes 

 (with barks, &c.) a jelly-like mass of pectic acid is obtained 

 by over saturating with ammonia, which prevents the precipitate 

 from subsiding, but may easily be dissolved in a gentle heat — col- 

 lect the pi-ecipitate on a filter, wash with water and redissolve in 

 dilute hydrochloric acid. Over-saturate the solution, if necessaiy 

 after filtering, with ammonia and immediately afterwards with acetic 

 acid, collect the deposit of pui'e oxalate of lime, dry at 100° and 

 weigh it. This lime-compound contains, if no oxalic acid has been 

 previously found, the whole of the oxalic acid contained in the 

 original vegetable substance. In 100 parts of it :z Ca O -f C 2 

 O3 -f 2 H O are contained 43.90 pai-ts oxalic acid. The oxalate 

 of lime may also be converted into carbonate of lime by heating to 

 a moderate red heat in an open crucible, and the oxalic acid may be 

 calculated from the latter salt; 100 parts Ca O + C O 2 corres- 

 pond to 72 parts oxalic acid. 



(b) Unite the liquid that has been sejiarated from the precipi- 

 tate efiected by ammonia, with the liquid that has been separated 

 from the pure oxalate of lime, over-satui-ate the mixture, if neces- 

 sary, with ammonia, allow the precipitate to subside, collect on a 

 filter, wash and dry. It consists chiefly of phosphate of lime and 

 phosphate of ammonio-magnesia, but may eventually contain traces 

 of alkaloids, met with in the preceding sections, or possibly an 

 alkaloid that has not been affected by extracting with ether, alco- 

 hol and water. Submit it therefore to the influence of warm 

 alcohol of 90%, filter and evaporate the filtrate. Any residue, 

 obtained hereby, has to be examined according to II., B, a. 



(c) Evaporate the liquid, left in b, to about 100 grams, in 

 order to remove the excess of ammonia and of water, and try with 

 a few sensitive alkaloid tests which are without influence on am- 

 monia-salts, viz., with tannic acid, chloride of gold, bi-iodide of 

 j:)otassium, iodide of potassio-mercury, iodide of potassio-bismuth, 

 phosphate of soda, chloride of mercury, nitrate of palladium. In 

 case of any turbidness, obtained, an alkaloid may be jjresent. 



Usually, for economy's sake, tannic acid is employed for preci- 

 pitating the whole liquid, if an alkaloid is supposed to be present. 

 Triturate the precipitate, obtained by tannic acid or by any other 

 of the above tests, after washing and while still moist, intimately 



* The acetic acid must be added immediately after the ammonia, be- 

 cause phosphate of lime and phosphate of ammonio-magnesia are only 

 soluble in acetic acid when newly precipitated. 



