MR. BRODIE ON CEROTIC ACID. 
151 
carefully prepared, it gave to analysis the following numbers. The analysis was 
made with chromate of lead. 
0*26 grm. of substance gave 0‘753 grm. of carbonic acid and 0‘307 grm. of water. 
These analyses give in 109 parts — 
Carbon .... 78*98 
Hydrogen . . . 13*12 
Oxygen .... 7 '90 
100*00 
This corresponds to the formula C54 H54 O4. 
C54 
H 
54 
O4 
Atomic weight. 
. 324 
54 
32 
410 
Calculated in 100 parts. 
79*02 
13T7 
7*81 
100*00 
It is very difficult to wash this lead salt perfectly out. Even in the present case, 
after the greatest care, I obtained a trace of a substance, soluble in ether, on attempt- 
ing further to purify the substance by combining it with baryta and washing out its 
baryta salt. This makes no difference in the numbers or the melting-point. But it is 
advisable to prepare the pure acid by boiling the acid as separated from the lead salt 
with caustic potash, precipitating the baryta salt by a large excess of chloride of 
barium, and carbonate of soda ; washing this well out with ether ; decomposing with 
an acid, and crystallizing the resulting substance repeatedly out of alcohol and ether. 
The acid prepared in this manner melted at 78°, 79° C., being the same melting- 
point as the acid separated from the lead salt ; it gave to analysis the following 
numbers : — 
I. 0*263 grm. gave 0*7583 carbonic acid and 0*3085 water. 
II. Another preparation. 0*2615 grm. gave 0*7558 carbonic acid and 0*307 water. 
III. 0*2612 grm. gave 0*7362 carbonic acid and 0*308 water. 
These analyses correspond in parts per cent, to — 
Carbon . . 
I. 
. . 78*63 
II. 
78*82 
III. 
78*95 
Hyd rogen 
. . 13*04 
13*04 
13*10 
Oxygen . . 
. . 8*33 
8*14 
7*95 
100 00 
100*00 
100*00 
The silver salt of this acid w^as made by precipitating the ammoniacal solution of 
the acid in alcohol with nitrate of silver. It is desirable to take an excess of am- 
monia, and the solution must be precipitated boiling by a hot alcoholic solution of 
the nitrate. The salt is to be washed with water and dried, first m vacuo, then in a 
water-bath. 
