Observations on Naphthaline. 15 
duct was carbonic acid : whether any water were formed, I could 
not ascertain. 
It cannot be irrelevant to the object of this paper to state, that 
the white concrete substance which I have been describing, has 
twice been observed by me in the form of minute crystals, which 
beautifully reflected the prismatic colours, in the neck of an 
earthen retort in which animal matter had been submitted to 
destructive distillation. 
Properties of the yellow Farina. 
From the minute quantity of this substance which I was ca- 
pable of obtaining, I could only ascertain one or two of its pro- 
perties. It is soluble in alcohol, and forms a solution of a bright 
yellow colour: and it is precipitable from the solution, by the 
addition of water, in the form of a yellow powder, which remains 
permanently suspended in the mixture. 
When heated, it melts into a substance of the consistence of 
a soft tough gum of a deep reddish brown colour. 
Of the four several substances which result from the distil- 
lation of the black liquid described in the former part of this 
paper, it is probable that the water and the yellow farina are the 
only real products, and that the others are mere educts of that 
distillation: for, with respect to the water, its proportion is va- 
riable according to the greater or less degree of rapidity with 
which the distillation is conducted; and if it were present as 
water in the black liquid, there is reason to believe it would be 
found supernatant on its surface, after having remained still for 
some time. ‘The essential liquid oil, and the white concrete sub- 
stance, which pass over during the distillation, are probably con- 
tained originally in that thin portion of the black liquid which 
may be filtered through unsized paper ; for the odour of this fil- 
tered portion closely resembles that of the oil; and the oil, by 
exposure to light, frequently becomes of a darker and darker 
shade, so as at last to he nearly of a deep brown colour; and 
with respect to the white concrete substance, this was not only 
found crystallized in that part of the original apparatus where 
the black liquid was condensed, but has been obtained from that 
liquid by simple evaporation of it at the common temperature of 
the atmosphere. 
The yellow farina is probably produced fron the tar which is 
contained in the proportion of about one-fourth in the black 
liquid ; for it does not make its appearance till towards the end 
of the distillation; when the more volatile substances have ceased 
to pass over, and the heat has been increased to the utmost : 
aud if common coal tar be exposed to a low red heat, it mi " 
ound, 
