ETHERS. 339 



Strontium lactate, Sr(C 3 H 5 3 ) 2 .3H 2 0, is readily obtained by dissolving 

 strontium carbonate in lactic acid. It is a white granular or crystalline 

 powder, readily soluble in water. 



45. ETHEKS. 



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 an alcohol radical by AIR, and an acid 

 radical by AcR, the general formula of an alcohol is A1R.OH, or 



TT /O, and of an acid, AcR.OH, or ^ ^O. 



Ethers are formed by replacement of the hydrogen of the hydroxyl 

 in alcohols by hydrocarbon residues (or alcohol radicals), and com- 

 pound ethers or esters 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 compound ethers to salts. For instance : 



Alcohol. Ether. Acid. Compound ether. 



It is not necessary that the two hydrocarbon residues in an ether 

 should be alike, as in the above ethyl ether, but they may be different, 

 in which case the ethers are termed mixed ethers. For instance : 



acid obtained from it? 434. Give properties of and tests for tartaric acid. 

 435. State the composition and formation of cream of tartar, Kochelle salt, 

 and tartar emetic. 436. What are Seidlitz powders, and what changes take 

 place when they are dissolved ? 437. Mention some official scale compounds 

 of iron, and give a general outline of the mode of preparing them. 438. 

 From what and by what process is citric acid obtained ? 439. Mention tests 

 by which citric acid may be distinguished from tartaric acid. 440. From 

 what and by what process is lactic acid obtained ; what are its properties ? 



