60 REPORT—1848. 
of the graphite used. The success of the oxidating process is greatly dependent on 
this preparation. Ground in the ordinary way, we have found 6 grains of pure 
graphite to require upwards of twelve hours for complete oxidation, while the same 
amount finely ground with silica was completely dissipated in about thirty minutes. 
3. Mixture.—With a retort of about 15 cubic inches we find 6 grains of graphite 
a convenient quantity to operate with. When prepared as above, it is to be mixed 
with 500 grains of powdered bichromate of potassa, and the whole being transferred 
to the retort, we add 1 cubic inch of water, and then pour slowly upon the mass 
5 cubic inches of sulphuric acid of the common density, taking care to mingle the in- 
gredients by gentle agitation as we add the acid. A moderate lamp-heat soon excites 
brisk reacticn, which is afterwards to be regulated by withdrawing or renewing the 
heat. At the close, the small tube attached to the tubulure of the retort is opened 
to permit aspiration, and a volume ef air, equal to two or three times the capacity 
of the retort, is drawn through the apparatus, 
Results.—The consistency of the results obtained by this method will be seen from 
the following examples, selected as fair specimens of a number of experiments per- 
formed in the same way :— 
Native Graphite.—A crystalline variety found in Albemarle county, Virginia. It 
occurs in long flat narrow plates of a curved form, packed closely together like the 
fibres of asbestus. 
6 grains of this mineral yielded— 
In the first experiment ..... sesseeesesseeees, Carbonic acid, 20°79 
» second  ,, sesesecssessecceeesss Carbonic acid, 20°82 
The mean corresponds in 100 grains to Carbon 94:56. 
Artificial Graphite or Kish.—In large crystalline plates with adhering iron and 
slag. The former was removed by digestion in acid, but some of the vitreous matter 
remained. 
6 grains of this substance yielded— 
In the first.experiment ......sss+seees2ee8. Carbonic acid, 16°58 
» second ,, sseecseseseseeeeeese Carbonic acid, 16°63 
The mean corresponds in 100 grains to Carbon 75:4 grains. 
To test the accuracy of the results, weighed specimens of graphite were carefully 
burnt to ash in a current of oxygen gas. The weight of carbon found by subtraction 
closely corresponded with that determined by the liquid process applied to the same 
specimen. 
It is proper to add, that the native graphite used in these experiments was first 
freed from any adhering carbonates or organic matter, by digestion in dilute sulphuric 
acid and subsequent ignition. 
We have made numerous experiments to test the applicability of this process for 
determining the carbon of coals. In the driest varieties of anthracite, the results 
presented a good degree of uniformity in repeated trials with the same specimen ; 
but wherever the coal contains a volatile compound of carbon, this is in greater or 
less part evolved without oxidation in virtue of the high temperature of the reaction. 
In the case of perfectly dry coke however the process gives uniform and accurate 
results, 
Oxidation of the Diamond in the Liquid Way. 
By Professors R. E. Rogers and W.B. RoceErs. 
The processes for oxidating the diamond hitherto described, consist in actually 
burning this gem, either in the air, in oxygen gas, or in some substance rich in oxy- 
gen, as nitrate of potassa. In all these experiments a very elevated temperature is 
required. We have therefore been much interested by discovering that the diamond 
may be converted into carbonic acid in the liquid way and ata moderate heat, by the 
reaction of a mixture of bichromate of potassa and sulphuric acid; in other words, by 
the oxidating power of chromic acid. This fact, although suggested in the progress 
of our experiments on graphite, was not unequivocally ascertained until lately. 
The method of proceeding is much the same as in the oxidation of graphite, but 
the progress of the oxidation is a great deal slower. 
——_a 
