268 . On the Tariareotis Salts. 



VI. 



Report made to the Clafs of Phjftcnl and Mathem'atital Sciences of the Injllttite of France'^ By 



Citizens GuYTon and VAVQ^VEtJU, dn a Afemoir of Citizen Thenord, entitled, " Oi- 



fe'rvations on the Combination of the 'Tartareous Acid, with the Salifiable Bafes, and the Pra- 



perties of the Salts ihus produced," * 



I 



T h^s long been known that the tartareous acid has a ftrong tendency to form triple 

 combinations ; among which the fait of Seignette, martial tartar, tartar emetic, and various 

 falls of this nature lifed m medicine are inftahcesi but Citizen Thenard has greatly added 

 to the number of thcfe combinations, by ofhers which have hitherto been unknown. 



Triple Salts, Alcaline and Earthy. 



The author was led -to thefe difcoveries by mixing folutions of lime, barltes, and ftron- 

 tian, with the folution of the acidulous tartrite of pot-afli. He remarks, that the firfb 

 portions of either of thefe earths produced no precipitation in the folution of tartrite of 

 pot-afli, and that no change is feen in the fluid till the moment when the excefs of the acid 

 of the cream of tartar approaches its term of faturation ; and that if this point be not ex- 

 ceeded, there will be formed on the fides of the veflel tranfparent cryftals, in which ana- 

 lyfis has {hewn him the prefence of tartareous acid, pot-a(h, and the earth in queftion. 



This firfl obfervation led him to prefume, that the tartareous acid may be fufceptible of 

 many other combinations of this kind, and the experiments we aie about to relate were 

 the confequences. , 



1. A combinatioti is formed between the tartrite of pot-afh and that of lime, from 

 which refults a fait with a double bafe foluble in waten This fa£t explains why no pre- 

 cipitate is afforded, when lime water is added to the tartrite of pot-afli, unlefs the quantity 

 be fuch as to exceed what is neceflary to form the triple fait. 



This fait may be obtained in the cryftalline form, if at the moment when the precipita- 

 tion begins to manifeft itfelf the fluid be left to Yepofe. A fhort time afterwards it be- 

 comes clear, and depofits on the furface of the glafs cryftals, of which Citizen Thenard 

 was not able to determine the figure. .'i,/ .;.ii <.«. .r.i , .■ ■• 



2. Analogous combinations take place between the tartrite of pot-afii, barltes, and ftron- 

 tian, each taken feparately. This is {hewn by the limpidity which the fluid preferves, fo 

 long as the mafs of the earths added does not exceed certain limits. Now as the author 

 remarks, this phenomenon cannot take place but by the cffed of a triple combination, be- 

 caufe the Ample and neutral union of the tartareous acid with either of thefe earths, falls- 

 down as foon as it is formed. 



3. The tartrite of magnefia has likewife a certain aflinity with the tartrite of pot-a{h, by 

 virtue of which they contraft an intimate union. The fait refulting does not cryftallize ; 



• Annale$ de Chimie, XXXVIII. 30* 



it 



