parts of gutta-percha, and 50 parts of paraffin, to which 20 parts of
magnesia and some mineral oil have been added.

* * * * *




CARBON IN STEEL.


At a recent meeting of the Chemical Society, London, a paper was read
entitled "Notes on the Condition in which Carbon exists in Steel," by
Sir F.A. Abel, C.B., and W.H. Deering.

Two series of experiments were made. In the first series disks of steel
2.5 inches in diameter and 0.01 inch thick were employed. They were all
cut from the same strip of metal, but some were "cold-rolled," some
"annealed," and some "hardened." The total carbon was found to be:
"cold-rolled," 1.108 per cent.; hardened, 1.128 per cent.; and annealed,
0.924 and 0.860 per cent. Some of the disks were submitted to the action
of an oxidizing solution consisting of a cold saturated solution of
potassium bichromate with 5 per cent. by volume of pure concentrated
sulphuric acid. In all cases a blackish magnetic residue was left
undissolved. These residues, calculated upon 100 parts of the disks
employed, had the following compositions: "Cold-rolled" carbon, 1.039
per cent.; iron, 5.871. Annealed, C, 0.83 per cent.; Fe, 4.74 per cent.
Hardened, C, 0.178 per cent.; Fe, 0.70 per cent. So that by treatment
with chromic acid in the cold nearly the whole of the carbon remains
undissolved with the cold-rolled and annealed disks, but only about