PYXIDICULA. 



[ C50 ] 



QUININE. 



an operculum. Several species ; fresh and 

 salt water. (Kent, Inf. 725.) 



PYXIDICULA, Ehr.— A genus of Dia- 

 toraacefe. 



Chca: Frustiiles 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. 



Kabenhorst reduces the species to P. major, 

 adriatica, and a doubtful form, P. Naeyelii. 



P. major (PI. 25. tig. 1.3). Valves coni- 

 cal, regularly punctate. Diameter 1-420" ; 

 freshwater. 



P. adriatica. Fr. se.-sile ; valves nearly 

 hemispherical, free from markings (ord. ill.). 

 Upon marine Algae. Diam. l-GOO". 



P. m{)ior=CycIotella operculata. 



The bodies represented in PI. 2o. fig. 12, 

 found in ilint, have been described as P. 

 (/lobator, Pritch. (not P. globosus, Ehr.) ; 

 they do not, however, appear to belong to 

 the Diatomacese. 



Kiitzing places Stephanopy.vis and Xan- 

 thiojyyxis here. 



BiBL. Ehr. Inf. 165, and Per. Perl. Ah. 

 1844 & 1845 ; Klitz. Bacill. 51, and Sp. AJfj. 

 21 ; Pritchard, Inf 432. 



PYXID'lUM, ' Kt.— Like Opercularia, 

 but solitary. Two species ; freshwater ; 

 on Entomostraca and Confervse. (Kent, 



Inf. asm:) 



PYXILLA, Grev. — A genus of Diato- 

 macese. 



BiBL. Grev. Mic. Trans. 1-865, 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 Feathebs, 



QUININE. See Alkaloids. 



lodo-disulp/iafe, sulphate of iodo-quinine, 

 Herapathite. — This remarkable salt is pre- 

 pared by dissolving disulphato of quinine in 

 strong acetic acid, warming the solution, 

 dropping into it an alcoholic solution of 

 iodine carefnily in small quantities at a 

 time, and placing the mixture aside for 

 some hours, when tlie 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 alt<n'ed, 

 that they are with diliiculty mounted. This 



may, howe-^-er, be effected by cautiously 

 neutralizing tlie excess of acid in the mother- 

 liquor b}' solution of ammonia, taking care 

 not to precipitate the excess of the disulphate 

 of quinine ; a portion of the liquid contain- 

 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 moimted 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. 



lierapath, 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 spii-it composed of equal bulks 

 of rectified spirit of sp. gr. 'SS? and dis- 

 tilled Avater ; and tincture of iodine, made 

 by dissolving 40 grains of iodine in 1 oz, of 

 rectified spu-it. The p-"oportion3 are : 



Disulphate of quinine. . 50 grains. 



Acetic acid 2 fiuid ounces. 



Proof spirit 2 fluid ounces. 



Tincture of iodine .... 60 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 imiform temperature of 45° to 50° F., 

 and kept from vibration. The latter may be 

 efll'cted by suspending the flask by the neck 

 witli 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 



