44 Mr. T. Taylor on some 



posure to the air becomes brown and turbid. The small quan- 

 tity of ellagic acid dissolved is precipitated by an acid. 



" Concentrated sulphuric acid readily dissolves these calculi 

 when assisted by a gentle heat. The solution is of a greenish 

 brown colour, and is precipitated by dilution with water. The 

 precipitate has the form of minute prisms arranged in stellate 

 groups ; the extremities of some of the prisms are blunt, others 

 are pointed. 



" When mixed with nitric acid, the ellagic acid calculus dis- 

 solves. If the acid be strong or slightly warmed, effervescence 

 takes place, nitrous fumes are given off, and a solution is pro- 

 duced of a beautiful pink-red colour, similar to that produced 

 by the action of nitric acid upon uric acid. The red colour 

 quickly disappears upon standing; on being heated, a deep 

 yellow solution remains, from which crystals of oxalic acid 

 may be obtained by evaporation. Ammonia added to the so- 

 lution causes it to assume a red colour, but does not render it 

 turbid. 



" The ellagic acid is best obtained from these calculi by dis- 

 solving the powdered calculus in a weak solution of caustic 

 potass, and transmitting through it a current of carbonic acid. 

 The precipitate which falls is to be digested in diluted muri- 

 atic acid, by which the potass is removed, and tolerably pure 

 ellagic acid remains. During the whole of the operation 

 great care must be taken to prevent the contact of atmospheric 

 air; for when dissolved in alkaline liquids, ellagic is quickly 

 converted into a species of ulmic acid. It is not improbable 

 that catechuic acid is sometimes present in these calculi. 



" This species of intestinal concretion appears to have been 

 first examined by Fourcroy and Vauquelin, and is included in 

 their class of resinous Bezoars*. It was shortly afterwards 

 examined by Berthollet, and subsequently by other chemists, 

 all of whom failed in deciding upon its true nature ; even so 

 recently as 1843 this calculus was described by M. Lippowitz 

 as consisting of a peculiar organic acid, for which he proposed 

 the name of Bezoaric acidf. 



" The concretions analysed by Berthollet, and of the proper- 

 ties of which he has given a very accurate account, had been 



* " La seconde variete d'une couleur brune ou violacee, sans saveur amere, 

 presque insoluble dans l'alcohol, cntierement soluble dans les alcalis, don- 

 nant dans cette derniere dissolution line liqueur qui devient rouge purpu- 

 rine, lorsqu'elle s'epaissit et se seche a l'air.- foumissant a la distillation un 

 sublime concret, jaune, d'une saveur et d'une couleur de suie, insoluble dans 

 l'eau et dans l'alcohol." — Annates du Museum National, torn. iv. 334. 



f Simon's Beitr'dge zur Phys. und Pathol. Chemie und Mikroskopie, B. i. 

 463. 



