476 Dr. Play fair on Palmic Acid. 



readily soluble in alcohol, which on evaporation yields palmic 

 acid of a yellow colour and still very impure. It is purified 

 by repeated crystallizations and pressure, and when quite 

 pure has a melting-point between 113° to 114° F. There re- 

 mains in the alcohol an uncrystallizable yellow oil, which be- 

 comes red on being saponified with caustic potash. 



Palmic acid, procured as described, is readily soluble in al- 

 cohol, from which it crystallizes, the crystals generally being 

 grouped together into clumps. From a fused state it solidi- 

 ties into stars, consisting of small crystals radiating from a 

 centre. The acid was burned with oxide of copper, and gave 

 the following results : — 



I. 0*074 grm. gave 0*2005 grm. carbonic acid, and 0*079 

 water. 



II. 0*128 grm. gave 0*3455 grm. carbonic acid, and 0*1365 

 grm. water. 



I. II. Mean. 



Carbon. . . . 73*89 73*61 73*75 



Hydrogen . . 11*86 11*84 11*85 



Oxygen . . . 14*25 14*55 14*28 



100*00 100*00 100*00 



In order to determine the atomic weight of the acid, the 

 silver salt was prepared in the following manner : — The pure 

 acid was boiled with a strong solution of pure carbonate of 

 potash, which it readily decomposes : on cooling, the soap se- 

 parated and was removed ; it was then dried and dissolved in 

 alcohol ; the solution of soap, after being separated from the 

 carbonate of potash, was filtered and evaporated to dryness in 

 a water-bath ; it was then dissolved in warm water and pre- 

 cipitated by an excess of nitrate of silver, the precipitate being 

 washed in the dark. 



Thus prepared, palmate of silver is a light white powder, 

 insoluble in alcohol and aether, but readily soluble in ammonia. 

 The following determinations of the amount of silver give the 

 data for estimating the atomic weight. 



I. 0*994 grm. salt left on ignition 0*271 silver. 

 II. 0*315 grm. salt left 0*0855 grm. silver. 



III. 0*3195 grm. salt left 0*0885 grm. silver. 



I. Silver = 27*26 per cent. 

 II. ... 27*14 

 III. ... 27*69 

 Mean . . . 27*36 

 This makes for the atomic weight of the silver salt 4937, and 

 for that of the acid contained in it, 3486. 



