bo IOWA ACADEMY OF SCIENCES. 



alcohol is given as .8021.* This would indicate either that 

 tlie alcohol was not absolute (the specific gravity obtained 

 corresponds to a 99 per cent, alcohol), or that the specimen 

 experimented upon was not quite pure. From the fact 

 that it gives the reaction of de Forcrand and Klepl men- 

 tioned above, one would be justified in concluding that the 

 latter was true, and that the alcohol was entirely anhydrous. 



Ethyl Alcohol, It has always been considered difficult 

 to remove the last traces of water from ethyl alcohol. On 

 account of the importance of absolute alcohol it was one 

 of the first subjects to receive the attention of the early 

 chemists and a number of good methods for dehydrating 

 ethyl alcohol were in use more than a century ago. In 

 the year 1788 the British government employed a chemist 

 by the name of Gilpin to work on the subject. He suc- 

 ceeded in obtaining alcohol of specific gravity .7939 at 60 

 degrees Farenheit. This was a remarkably good result for 

 that time. The specific gravity of ethyl alcohol is now 

 usually considered to be .7938. One experimenter,f how- 

 ever, claims to have prepared an alcohol of specific gravity 

 .7935. 



The common dehydrating agents for ethyl alcohol are 

 calcium chloride (for removing the first portion of water), 

 anhydrous potassium carbonate, anhydrous potassium 

 acetate, anhydrous copper sulphate, metallic sodium, phos- 

 phoric anhydride, barium oxide, and calcium oxide. Drink- 

 water,:!: about 1860, and Mendeleeff,§ in 1865, showed that 

 calcium oxide was superior to all dehydrating agents then 

 in use. 



The term "absolute alcohol" is frequently used to indi- 

 cate any alcohol that is stronger than can be obtained by 

 simple fractional distillation and which still contains con- 

 siderable water. Most of the absolute alcohol of the best 

 grade contains some water. A specimen at hand from 

 Sargent & Company evolves some acetylene when warmed 

 with powdered calcium carbide. 



•Allen's Com. Org. Anal. , Vol. I, page 71. 



+Allen's Com. Org. Anal. , Vol. I, page 85. 



tDr. Sheridan Musprat's Chemistry, Vol. I, pages 51-52. 



$Jour. Lond. Chem. Soc. , 1871, 133. 



