the Purity of the Sulphate of Quina. 113 



6thly. A repetition of the above process, substituting alco- 

 hol for water, answers for extracting resin and some other 

 substances, because sulphate of quina is soluble in alcohol to 

 only a limited extent. 



7thly. If a white substance insoluble in cold water be found 

 in the sulphate 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. 



8thly. Sulphate of quina has been adulterated with ammo- 

 niacal salts. These are rendered obvious by adding a little 

 of the suspected salt to a solution of potash. If any ammo- 

 niacal salt be present, ammoniacal gas will be readily detected, 

 either by the smell, or by holding over the mixture 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 inde- 

 structible by heat, will of course remain in the vessel. 



lOthly. To ascertain that the sulphate of quina contains 

 the proper quantity of sulphuri cacid 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 lo grains of nitrate 

 of barytes, and separate the precipitated sulphate of barytes 

 by filtering. If nitrate of barytes be now added to the clear 

 solution, it should still occasion slight precipitation, for 60 of 

 sulphate of quina contain 5*8 gr. of sulphuric acid, equiva- 

 lent to 19*1 of nitrate of barytes. 



This test is only to determine that there is no crystallized 

 vegetable matter uncombined with sulphuric acid in the sul- 

 phate of quina ; the detection of earthy or alkaline sulphates 

 has already been provided for. 



llthly. Sulphate of quina should lose not more than from 

 8 to 10 per cent of water by being heated till deprived of its 

 water of crystallization. Mr. Barry informs me that he once 

 examined a sample which contained more than 40 per cent of 

 water in excess diffused through it. 



New Series. Vol. 3. No. 14. Feb. 1828. Q XIX. On 



