Zeise on the Hydroxanthic Acid. 305 



abundance above the edges of the vessel. The capsule is then 

 put immediately under the receiver of an air-pump, and a partial 

 vacuum is made. When it is judged that the excess of car- 

 buret of sulphur with a portion of alcohol has been removed, he 

 introduces a vessel containing sulphuric acid, and sets tlie pump 

 in full action. At the end of some time he withdraws the vessel 

 with the sulphuric acid, and replaces it by another of the same, 

 till there remains very little liquid in the vessel containing the 

 salt. Then, some time after, adding a little pure sulphuric 

 ether, he throws the mass on a filter ; a little thereafter he 

 presses it quickly between folds of paper, and finishes the 

 desiccation under the air-pump receiver. In winter, or ia 

 case we have plenty of ice at our disposal, he thinks the pre- 

 paration cf this salt may be effected by simple refrigeration. 

 Evaporation in the open air has this disadvantage, that a part of 

 the salt commonly assumes a yellow colour, and then it yields a 

 solution more or less milky. We must take care not to employ 

 too concentrated a solution of potash in alcohol ; otherwise we 

 obtain almost immediately a congealed mass, and here it may 

 happen that a trace of sulphuretted hydrogen shall be formed. 



Hydroxanthate of Potash. — This salt crystallizes in needles ; 

 it is colourless and very brilliant ; in the air, it becomes faintly 

 yellowish ; it has a peculiar smell ; its taste, at first, extremely 

 cooling, becomes sulphureous and pungent. It is extremely so- 

 luble in water, and yet it does not attract humidity from the air. 

 When newly prepared it dissolves completely in alcohol, but less 

 copiously than in water; sulphuric ether dissolves very little of it, 

 and petroleum does not aflfect it. A solution of this salt becomes 

 milky by contact of air, and at the same time slightly alkaline. 

 Hence test-papers, which on leaving a solution of hydroxanthate 

 indicated no free alkali, change colour in the space of some time 

 in the air. 



On pouring acetic muriatic, or sulphuric acid, even in a 

 very concentrated state, on the hydroxanthate of potash, no 

 effervescence takes place ; but the latter two acids, diluted with 

 four or five waters, separate from it a liquid which is heavier 

 than water, and in aspect perfectly resembling an oil. This is 

 the hydroxanlhic acid. 



Barytes water, muriate, or nitrate of barytes, muriate of lime, 

 sulphate of magnesia and alum, form no precipitates in a Avatery 

 solution of the hydroxanthate of potash; sulphate of zinc, nitrate 

 or acetate of lead, deutochloride or deutocyanide of mercury, 

 produce white precipitates. With sulphate, nitrate, or muriate 

 of copper, it occasions a precipitate of a very beautiful yellow 

 colour. Chloride of antimony, nitrate of bismuth, deutochloride 

 of tin, protochloride of mercury, and nitrate of silver, form also 

 with it precipitates, which are of a yellow colour. 



The precipitates by nitrate of silver, or protochloride of mer- 

 X2 



