Chemistry. 37S 



phate of quina will be deposited in feathery crystals in twenty-four hours, 

 if there be no adulteration. 



2dly, As indirect, but as good collateral evidence, the taste of sulphate 

 of quina of known good quality may be compared with that of another 

 sample. Thus when purei a grain of sulphate of quina will render nearly 

 a pound and a-half of water, or 10,500 grains, sensibly bitter. 



Sdly, The alkalies either pure or their carbonates, if but slightly in ex- 

 cess, always occasion precipitation at ordinary temperatures in a solution 

 of sulphate of quina containing only 1-lOOOth of its weight, or less than 

 one grain in two fluid ounces of water. 



Aithly, A solution of tannin occasions a very sensible precipitate in an 

 aqueous solution of sulphate of quina, containing only l-10,000th of its 

 weight of the salt, provided there be no acid in excess. Kino is that form 

 of tannin which best answers the purpose. It is, however, to be observed, 

 that the salts of morphia, cinchonia, strychnia, &c. are similarly affected 

 by tannin ; but they are not likely to be mixed with sulphate of quina. 



5thlyj Sulphate of quina suspected to contain sugar, gum, or other sub- 

 stances soluble in cold water, may be tried by digesting the same portion 

 of the salt in small and successive portions of water to saturation. If the 

 sulphate of quina be pure, and the solutions all properly saturated, they 

 will have the same taste and specific gravity ; and similar portions will 

 yield by evaporation equal quantities of solid residuum. 



Gthlyj A repetition of the above process, substituting alcohol for water, 

 answers for extracting resin and some other substances, because sulphate 

 of quina is tcoluble in alcohol to only a limited extent. \ 



'Uhly, If a white substance insoluble in cold water be found in the sul- 

 phate of quina, heat the mixture to about 170" of Fahrenheit. This will 

 render starch soluble, and its presence may be determined by the addition 

 of an aqueous solution of iodine, which will immediately occasion a blue 

 colour, and eventually a blue precipitate. The iodine should be added in 

 very small quantity. 



Sthly, Sulphate of quina has been adulterated with ammoniacal salts. 

 These are rendered obvious by adding a little of the suspected salt to a 

 solution of potash. If any ammoniacal salt be present, ammoniacal gas 

 will be readily detected, either by the smell, or by holding over the mix- 

 ture a piece of turmeric paper, or a bit of glass moistened with acetic acid. 



9thly, To ascertain whether sulphate of quina contains any earthy salts> 

 such as sulphate of magnesia or sulphate of lime, burn a portion of it in 

 a silver or platina crucible, or even in a clean tobacco-pipe. Any earthy 

 salt, or any matter indestructible by heat, will of course remain in the 



lOikly, To ascertain that the sulphate of quina contains the proper 

 quantity of sulphuric acid and quina, dissolve a little in pure muriatic or 

 nitric acid, and add a solution of muriate or nitrate of barytes ; 60 parts 

 should give about 17.3 to 17.4 of sulphate of barytes; or the method may 

 be varied without the trouble of drying the precipitate. Dissolve 60 

 grains of sulphate of quina in water slightly acidulated with muriatic or 

 nitric acid ; add a solution of 18 grains of nitrate of barytes, and separate 

 the precipitated sulphate of barytes by filtering. If nitrate of barytes be 



