C. M. Warren on Sulphur in Organic Compounds. 41 
rpose. 
he combustion-tube being packed with pure asbestus be- 
tweeen the points a an ' 
6, fig. 1, and the space— 
abouttwoinchesin length 
—between 5b and ¢ left 
vacant, a plug of pure as- 
tus is placed at c, an 
the space between c and d, about three or four inches in length, 
then filled with a mixture of pure asbestus and peroxyd of lead, 
and finally a plug of asbestus is placed at d. As the sulphuric 
acid formed is to be absorbed by, and finally determined from, 
the peroxyd of lead,—in order to obviate the necessity of treat- 
ing the whole of the asbestus in the tube to obtain the sulphuric 
acid, which would be troublesome, and at the same time preserve 
the asbestus packing in the posterior part of the tube in a fit 
Condition for future use,—it is important that the asbestus plug 
at c should be packed closely enough to prevent any particles 
the peroxyd of lead from passing back of this plug. : 
As already stated, the object of mixing asbestus with the per- 
oxyd of lead is to prevent the formation of a channel along the 
top. In this manner but a short column of the mixture of as- 
tus and peroxyd of lead will suffice to secure complete con- 
Version of the sulphurous acid. The combustion is conducted 
recisely as for the determination of carbon and hydrogen alone, 
except that the portion of the tube which contains the peroxyd 
of lead is maintained at a gentle heat, sufficient to prevent con- 
densation of water in that part of the tube and at the cork, but 
avoiding a temperature which would decompose the peroxyd of 
lead. As usual, the water formed is absorbed in a chlorid of 
itself, s0 heavy a der. Through such a channel sulphurous acid might pass, in 
small propiation, Without coming in contact with the peroxyd of lead. It will 
seen that the liability to the formation of a — is a m Sage 
d of lead with a large ‘ion of asbestus. asbestus serves 
also to real soa the parauity of ts eight ae in this manner — to lessen the 
T may here add that, in making the combustion with oxygen in presence of asbestus, 
acid reaches the 
the quantity of sulphurous acid which peroxyd of lead is by no means 
very large.” In a piel inary experiment, in which carbonate of soda was 
instead of peroxyd of lead, (the substance burnt being bisulphid of carbon), the 
carbonate of soda o contain within about 9 per cent of the equivalent of 
nad and a portion o: i it isnot unlikely may bave been taken up 
a that was employed in this instance. iy 
Concerning the other source of art to the determination of carbon which Carius 
mentions, it will suffice to remark that, in my process, the peroxyd of lead is kept 
oe & temperature that the absorption of carbonic acid appears to be pre- 
AM. Jour. 8c1.—Szoonp Sexms, Vou. XLI, No. 121.—Jax., 1866. 
, 6 
