960 OILY ACIDS. 



and inodorous, fused by heat or dissolved in alcohol it reddens 

 litmus ; it dissolves in its own weight of ether of density 0.727, 

 when heated in air it burns like wax. Stearic acid is decom- 

 posed by dry distillation, and resolved into margaric acid and 

 oxide of margaryl. Nitric acid with heat decomposes it pro- 

 ducing first margaric acid, and afterwards suberic and succinic 

 acids. Stearic acid is dissolved entirely by sulphuric acid with 

 a gentle heat, without coloration, and is precipitated on the 

 addition of water in the form of white flocks. It may thus be 

 separated from sulphate of glyceryl, and in a great measure 

 from oleic acid. 



Stearates. Stearic acid is bibasic and forms two classes of 

 salts in which one or both of its basic atoms of water are re- 

 placed by a metallic oxide. In the cold, stearic acid only 

 decomposes the alkaline carbonates partially, so as to produce 

 a bistearate and bicarbonate, but with heat it decomposes the 

 same carbonates completely. The neutral stearates of alkaline 

 bases dissolve without alteration in 10 or 20 parts of hot water, 

 but the addition of a large quantity of water causes decompo- 

 sition, and an acid stearate precipitates while the liquid becomes 

 strongly alkaline ; the cooling of a hot solution of a stearate in 

 a small quantity of water is attended with the same decomposi- 

 tion, and causes the whole mass to assume a gelatinous con- 

 sistence. The acid stearate of potash contains HO + KO as 

 base ; obtained by precipitation of the neutral stearate in 

 solution by 1000 parts of cold water, and crystallized from 

 alcohol it forms white pearly plates. Boiling water still farther 

 decomposes this stearate, 1000 parts of the former producing 

 with the latter a turbid and viscid liquid, which becomes liquid 

 and transparent at 167, and deposits pearly plates between 

 138.2 and 78.8 (59 to 26 centig.) ; 3 atoms of the acid salt 

 are then resolved into 1 atom of the neutral stearate of potash 

 (containing 2KO as base) which remains in solution, and into 

 a bistearate of potash (containing KO + 3HO as base to 2 atoms 

 of acid), which remains in suspension in the liquid. Again, by 

 the cooling of the solution of the neutral stearate of potash, a 

 portion of the former acid stearate of potash is deposited, and 

 half of the alkaline base remains in solution. The precipitate 

 is therefore a mixture of bistearate and acid stearate of potash. 

 If exposed again to boiling water it ends by being converted 



