104 
Proceedings of the Royal Society 
propionic acid. These two bodies possess such different properties, 
that they may be at once and with certainty recognised. 
The task, therefore, which I set myself, was, by the assistance of 
the chlorinated acid, to determine the position in the molecule 
of the alcoholic hydroxyl. Thebo-lactate of lime, dried at 150°, was 
treated with perchloride of phosphorus in the proportion of two 
molecules of the latter to one of the former. This mixture was 
heated in a retort, attached to the lower end of a Liebig’s condenser, 
until the disengagement of hydrochloric acid ceased, when the 
condenser was reversed and the volatile products distilled off. By 
this means the decomposition is so complete that the residue, con- 
sisting of chloride of calcium, may be heated until the glass of the 
retort softens without carbonising to any very sensible extent. 
The distillate was separated by rectification up to 111° into a residue, 
which did not distil without partial decomposition, and a distillate. 
The latter was treated with the necessary precautions* with water, 
to obtain the chlorinated acid, and the former with absolute alcohol, 
to obtain its ether. 
The acid thus obtained possessed all the properties of that formed 
from ordinary lactic acid. A chlorine determination gave 32'95 
per cent, chlorine. The theoretical amount calculated from the for- 
mula C S H 5 C10. 2 is 32-72. Its specific gravity is 1*27, against 1*28 
found for the acid derived from ordinary lactic acid. It passed 
entirely between 185° and 186°; the boiling point of a- chloropro- 
pionic acid is 186°. The two acids have also the same outward 
appearance, being colourless, uncrystallisable liquids, possessing the 
same smell, and exercising the same corrosive action on the skin, 
unaccompanied by pain or blisters. 
The ether also possesses exactly the same properties as that pre- 
pared from ordinary lactic acid. A chlorine determination gave 
26-34 instead of 26 , 01 per cent, demanded by the formula C 5 Ii 9 C10 2 . 
They both boil at 144°, and have the same smell ; they are also 
both formed with great ease by heating their acids with alcohol and 
sulphuric acid. 
It is thus evident that the chlorinated acids obtained by the same 
means from the two acids under comparison are identical. The 
chlorine, therefore, in both cases, is united to the same carbon atom, 
* Compt. Rend. lxvi. 1157. 
