2 DR. ANGUS SMITH ON THE COMPOSITION 
from the operation of manufacturing the disinfecting pow- 
der called by his name, where carbolic acid or kreasote 
from coal is used. When he observed this red colour 
he renewed the surface of the lime and obtained a fresh 
portion. By continual renewals in this manner he ob- 
tained a crust of a very deep colour. This he brought to 
me. There were several pounds weight of it; but al- 
though the colour appeared so deep, a very small portion 
of colouring matter was found. 
When this lime compound was heated with alkalies, a 
portion of the colouring matter was removed. I used 
ammonia, but soda or potash answered the same purpose. 
It was, however, not possible, or at least it was exceedingly 
tedious, to remove the whole in this manner, and when the 
lime was dissolved by muriatic acid, a black resin was 
found first swimming in a melted state in the rather warm 
liquid, and afterwards sinking and cooling, a dark resinous 
substance. The power of giving colour was remarkable, 
as I did not obtain more of this resin than about an ounce 
to a hundredweight of the lime compound. Of course 
the colour in these cases led me to think of Runge’s 
rosolic acid, which he has described in 1834 in Poggen- 
dorff’s Annalen (vol. xxxi. p. 70) in the following manner : 
** Rosolic acid, or rosadleic acid (Rosolsaure oder Rosadl- 
siure), is a product of the chemical decomposition of coal 
oil, and is so much the more remarkable on account of 
acting like a true pigment. With a suitable mordant it 
gives colours and lakes before which those of safflower, 
eochineal and madder must give way. 
“ Rosolic acid is a resinous mass, which may be reduced 
to a powder; it possesses a beautiful orange colour. I 
have not been able to find in the coal oils the substance 
from which it is produced; but to show its existence it is 
only necessary to shake the oil with milk of lime, to filter, 
and to boil for a few hours. The solution, at first colour- 
