518 CONSIDERATION OF CARBON COMPOUNDS. 



nitric acid is set free; the insoluble bismuth citrate is collected, washed, and 

 dried; it forms a white, amorphous powder, which is insoluble in water, but 

 soluble in ammonia water. 



Bismuth ammonium citrate is a scale compound obtained by dissolving bismuth 

 citrate in ammonia water and evaporating the solution at a low temperature. 



Ferric citrate, Ferri citras. Obtained in transparent, red scales, by dissolving 

 ferric hydroxide in citric acid and evaporating the solution as mentioned here- 

 tofore. By mixing solution of ferric citrate with either ammonia water or 

 quinine, strychnine, sodium phosphate, or sodium pyrophosphate, evaporating 

 to the consistence of syrup and drying on glass plates, the following scale com- 

 pounds are obtained respectively : Iron and ammonium citrate, iron and quinine 

 citrate, iron and strychnine citrate, soluble ferric phosphate, and soluble ferric pyro- 

 phosphate. 



47. ETHERS AND ESTERS. 



Constitution. It has been shown that alcohols are hydrocarbon 

 residues in combination with hydroxyl, OH, and that acids are hydro- 

 carbon residues in combination with carboxyl, CO.OH ; it has further 

 been shown that carboxyl may be considered as being composed of 

 CO, and hydroxyl, OH, and that the term acid radical is applied to 

 that group of atoms in acids which embraces the hydrocarbon residue 

 -f- CO. If we represent a hydrocarbon radical by R, and an acid 

 radical by R.CO, the general formula of an alcohol is R.OH, or 



^>O, and of an acid, R.CO.OH, or R ' C >O. 



Ethers are formed by replacement of the hydrogen of the hydroxyl 

 in alcohols by hydrocarbon residues, and esters, also called compound 

 ethers, or ethereal salts are formed by replacement of the hydrogen of 

 the hydroxyl (or carboxyl) in acids by hydrocarbon residues. While 

 alcohols correspond in their constitution to hydroxides, ethers corre- 

 spond to oxides, and esters to salts. For instance : 



QUESTIONS. Name the more common organic acids found in vegetables 

 and especially in sour fruits. What is the composition of oxalic acid, how is 

 it manufactured, and what are its properties? Explain the formation of crude 

 tartar during the fermentation of grape-juice, and how is tartaric acid obtained 

 from it? Give properties of and tests for tartaric acid. State the composition 

 and formation of cream of tartar, Rochelle salt, and tartar emetic. What are 

 Seidlitz powders, and what changes take place when they are dissolved ? Give 

 the general composition of hydroxy-acids, and state a method for preparing 

 them synthetically. From what and by what process is citric acid obtained ? 

 Mention tests by which citric acid may be distinguished from tartaric acid. 

 From what and by what process is lactic acid obtained ; what are its prop- 

 erties ? 



