PYXIDICULA. 



[ 050 ] 



QUININE. 



an operculum. Several species ; fresh and 

 salt water. (Kent, Inf. 725.) 



PYXIDIO'ULA, Ehr. A genus of Dia- 

 tomacene. 



Char. Frustulea single, free or sessile ; 

 valves circular, convex, hoop absent. 



Numerous species have been described 

 one f r. wat., one marine, the remainder fossil, 

 found in America. 



Ilabenhorst reduces the species to P. major, 

 adriatica, and a doubtful form, P. Naeyelii. 



P. major (PL 25. fig. 13). Valves' coni- 

 cal, regularly punctate. Diameter 1-420" ; 

 freshwater. 



P. adriatica. Fr. sessile ; valves near y 

 hemispherical, free from markings (ord. ill ). 

 Upon marine Algae. Diam. 1-000' '. 



P. minor=Cyclotella operculata. 



The bodies represented in PL 25. fig. 12, 

 found in flint, have been described as P. 

 globator, Pritch. (not P. ylobosm, Ehr.) ; 

 they do not, however, appear to belong to 

 the Diatomaceae. 



Kiitzing places Stephanopyxis and Xan- 

 thiopyxis here. 



BIBL. Ehr. Inf. 165, and Her. Berl. Ak. 

 1844 & 1845 ; Kiitz. Bacill.ol, and Sp. Alg. 

 21 ; Pritchard, Inf. 482. 



PYXID'IUM, Kt. Like Operctdaria, 

 but solitary. Two species ; freshwater ; 

 on Entomostraca and Confervas. (Kent, 

 Inf. GOG.) 



'PYXILLA, Grev. A genus of Diato- 

 macene. 



BIBL. Grev. Mic. Trans. 1865, 2. 



Q. 



QUARTZ. See ROCKS. 



QUILL. The quill of feathers possesses 

 considerable polarizing power; the coloured 

 bands, however, are so broad that they are 

 better seen with the naked eye. 



See FEATHERS. 



QUININE. See ALKALOIDS. 



lodo-disulphate, sulphate of iodo-quinine, 

 Herapathite. This remarkable salt is pre- 

 pared by dissolving disulphate of quinine in 

 strong acetic acid, warming the solution, 

 dropping into it an alcoholic solution of 

 iodine carefully in small quantities at a 

 time, and placing the mixture aside for 

 some hours, when the crystals separate. 



They dissolve in the heated mother-liquor, 

 also in hot alcohol, being again deposited 

 on cooling ; but they are not soluble in cold 

 alcohol or ether. 



They are so easily decomposed and altered, 

 that thev are with difficulty mounted. This 



; may, however, be effected by cautiously 

 i neutralizing the excess of acid in the mother- 

 liquor by solution of ammonia, taking care 

 ; not to precipitate the excess of the disulphate 

 j of quinine ; a portion of the liquid contain- 

 j ing the crystals is then transferred to a slide, 

 the liquid removed with blotting-paper, and 

 the crystals dried in a current of cold air. 

 They are then mounted in Canada balsam, 

 rendered thin with ether, heat being avoided. 

 The crystals are of a pale olive-green 

 colour (PI. 11. fig. 17), and possess a more 

 intense polarizing power than any other 

 known substance. The play of colours pre- 

 sented when they are rolling over each other 

 whilst contained in a watch-glass, forms a 

 very beautiful sight, the colours varying 

 according to the relative positions of the 

 crystals to each other ; and when the latter 

 cross each other at a right angle, complete 

 blackness is produced. 



Herapath, who discovered this beautiful 

 salt, has described a method of making 

 crystals of sufficient size to replace tourma- 

 lines or Nicol's prisms. The ingredients 

 are : as pure disulphate of quinine as can 

 be obtained, that from Howard and Kent 

 being best ; strong acetic acid, of sp. gr. 

 1'042 ; proof spirit composed of equal bulks 

 of rectified spirit of sp. gr. *837 and dis- 

 tilled water ; and tincture of iodine, made 

 by dissolving 40 grains of iodine in 1 oz. of 

 rectified spirit. The proportions are : 



Disulphate of quinine. . 50 grains. 



Acetic acid 2 fluid ounces. 



Proof spirit 2 fluid ounces. 



Tincture of iodine .... 50 drops. 



The disulphate of quinine is dissolved in the 

 acetic acid mixed with the spirit, the solu- 

 tion heated to 130 F., and the tincture of 

 iodine immediately added in drops, the 

 mixture being constantly agitated. 



The compound should be prepared in a 

 wide-mouthed Florence flask ; and the tem- 

 perature should be maintained for a little 

 time after the addition of the iodine, so that 

 the solution may become perfectly clear, 

 and of a dark sherry-colour. It should 

 then be set aside to crystallize in a room of 

 a uniform temperature of 45 to 50 F., 

 and kept from vibration. The latter may be 

 effected by suspending the flask by the neck 

 with strong string, attaching this to a hori- 

 zontal cord stretching across the room from 

 one wall to the other ; or placing the flask 

 on a steady support, lying upon a pillow. 

 The large crystalline plates form upon the 



