452 
MR. T. H. LABY ON THE SUPERSATURATION AND 
liquids for which these have been found. Young and Thomas* have determined a 
number of constants for ten carefully purified esters. The data required exist or can 
he calculated for the formic to iso-valeric series of acids. A study of these esters and 
acids shows how homologous and isomeric compounds behave. 
Liquids used. 
All the liquids used were Kahlbaum’s preparations. They were fractionated with 
a 12-bulbed (pear-shaped) still-head. The boiling-points, at 760 mm. pressure, given 
differ from those obtained by Young and Thomas and others partly on account of 
errors of the writer’s thermometers. A more reliable criterion of purity is constancy 
of boiling-point. 
Methyl formate: Dried with phosphorus pentoxide and then fractionated from it. 
The fraction used boiled from 31°'8 to 31°*9 C. (31° - 9 C. Young and Thomas). 
Methyl acetate : Dried with phosphorus pentoxide and fractionated from it. After 
three fractionations the portion boiling at 56 0, 9 (57°*15 to 57°'3 Young and Thomas) 
was collected and used. 
Ethyl acetate : Fractionated from phosphorus pentoxide, the first portion rejected 
and that boiling at 77°T (77 0, 15 Young and Thomas) was collected. 
Propyl acetate: Dried with phosphorus pentoxide; fractionated twice. The 
slightly hydrolysed distillate was treated with potassium carbonate, and then with 
phosphorus pentoxide, and distilled. Boiling-point 101 o- 4 to 101 o, 9 (101 o- 35 Young 
and Thomas). 
Methyl butyrate: Fractionated; the portion boiling at 102 o, 9 (l02 o, 8 Young and 
Thomas) was distilled from phosphorus pentoxide. 
Methyl iso-butyrate : Fractionally distilled, treated with phosphorus pentoxide, and 
distilled, then with potassium carbonate, followed by phosphorus pentoxide. Boiling- 
point 92°*4 to 92°-6 (92 0, 3 Young and Thomas). 
Ethyl propionate: Distilled from phosphorus pentoxide, and redistilled. Boiling- 
point 98°’9 to 99°'G (99° Young and Thomas). 
Formic acid, : Kahlbaum’s best acid was used direct from the sealed glass flask it 
was supplied in. Boiling-point 101 0 * I (Richardson 101 o, 3, Schmidt 100 o, 4, Roscoe 
101°, Perkin 101°). 
Acetic acid: Fractionated five times; final fraction boiled at 118°*5 to 118°‘6, but 
the freezing-point appeared low, indicating the presence of water. The stock acid 
was then three times crystallised, twice distilled ; it then gave a boiling-point of 
118° to 118°'05 (118 C 5 Young’s “ Fractional Distillation”), and a freezing-point of 
1 6 *5 (16°'6 Holleman’s “ Organic Chemistry”). 
Propionic acid was distilled from phosphorus pentoxide, and twice fractionated. 
The portion used boiled from 138 0- 9 to 139 0, 1 (l40 o, 3 Richardson). 
* ‘Trans. Chem. Soc.,’ 63, 1220 (1893). 
