292 CONSIDERATION OF CARBON COMPOUNDS. 



bicarbonate, causing the formation of sodium tartrate, while the 

 escaping carbon dioxide causes effervescence. 



Antimony potassium tartrate, Antimonii et potassii tartras, 

 2(KSbO.C 4 H 4 6 ).H 2 = 664 (Tartrate of antimony and potassium,, 

 Tartar emetic}. This salt is made by dissolving freshly prepared 

 antirnonious oxide (while yet moist) in a solution of potassium 

 acid tartrate. From the solution somewhat evaporated, tartar 

 emetic separates in colorless, transparent rhombic crystals: 



2(KHC 4 H 4 O 6 ) + Sb 2 O 3 = 2K.SbO.C 4 H 4 6 + H 2 O. 



Potassium Antirnonious Tartar emetic, 



acid tartrate. oxide. 



The fact that not antimony itself, but the group SbO replaces 

 the hydrogen, has led to the assumption of the hypothetical 

 radical SbO, termed antimonyl. 



Tartar emetic is soluble in water, insoluble in alcohol; it has 

 a sweet, afterwards disagreeable metallic taste. 



Action of certain organic acids upon certain metallic oxides. The 

 solution of a ferric salt (or certain other metallic salts) is pre- 

 cipitated by alkaline hydrates, a salt of the alkali and ferric 

 hydrate being formed. When a sufficient quantity of either 

 tartaric, citric, oxalic, or various other organic acids has been 

 previously added to the iron solution (or to certain other metallic 

 solutions), no such precipitate is produced by the alkaline 

 hydrates, because organic salts or double salts are formed which 

 are soluble, and from which the metallic hydrates are not pre- 

 cipitated by alkaline hydrates. Upon evaporation no crystals 

 (of the organic salt) form, and in order to obtain the compounds 

 in a dry state, the liquid, after being evaporated to the consist- 

 ence of a syrup, is spread on glass plates which are exposed to 

 a temperature not exceeding 60, when brown, green, or yel- 

 lowish-green, amorphous, shining, transparent scales are formed, 

 which are the scale compounds of the U. S. P. 



Instead of obtaining these compounds, as stated above, by 

 adding the organic acids (or their salts) to the inorganic salts, 

 they are more generally obtained by dissolving the freshly pre- 

 cipitated metallic hydrate in the organic acid. 



The true chemical constitution of many of these scale com- 

 pounds has as yet not been determined with certainty. 



