THE DETERIORATION OF COAL.
I O 27
able percentage of loss. The presence of tellurium in the bead does not necessarily imply a loss of gold in the cupellation though, of course, a frosted bead would not be permissible when silver is to be determined. In high-grade tellurides when silver is t o be estimated, the writer suggests a preliminary treatment with nitric acid, with subsequent precipitation of the silver a s chloride which may be dried and added with the residue from the acid treatment to the fluxes in the crucible. Variation in temperature of fusion does not seem to be of great moment though the data above are most favorable to a temperature of about 1200'. The average obtained from Series No. I is higher than that obtained in the others showing a loss due to tellurium in fusion and cupellation, yet the variation is small, the average of No. I being not more than 0.24 per cent. higher than the lowest average, t h a t of Series No. 2 . The members of the various series differ among themselves in some cases considerably, but perhaps not more than would b-, expected i n any highgrade ore, owing to lack of homogeneity of sample. In the opinion of thc writer, irregularities in high-grade tellurides are due more to this lack of homogeneity than to tellurium. I t is conceivable that in some ores the ratio of gold t o tellurium might be much less and hence the percentage of loss greater. In such cases a preliminary treatment with nitric acid to remove the tellurium would obviate the difficulty. UNIVERSITY OF LINCOLN,
NEBRASKA, NEB.
THE DETERIORATION OF COAL. BY S. W . PARKA N D W. F. WHEELER. Received April 7, 1908.
In cooperation with the State Geological Survey and the Engineering Experiment Station of The University of Illinois, certain facts have developed which bear directly upon the behavior of coal. They are of considerable moment and should be taken into account in any study of this material. The first pertains to a deterioration which cannot be ascribed t o weathering processes, but rather to the simple fact of the release of the material from the conditions which have surrounded it in the seam. This has been recognized in a rather indefinite may from time to time, but without data t o substantiate the fact.' The following items are given in support of this theory of loss. In the summer of 1900 twenty-nine samples of coal were collected a t the face of the vein, quartered in the usual manner, placed i n galvanized iron cans with screw cap and tire-tape seal, exactly as described by the Coal Testing Plant of the United States Geological Survey.* They were
* THISJOURNAL, 28, 6 j o
(1906).
Bulletin No. 261,of the Cod Testing Plant, 11. S. G. S.
S. Li'.
10.8
I'.2RR
.\SI) W. P. WHEELER.
shipped directly to the laboratory, where they were transferred a t once to one-quart jars of the ' ' Lightning" or Putnain type, the coal being sufficient to practically fill the jars. 'This transfer was made with as much as possible of the original inoisturc retained in the coal. The " Lightning" jars were chosen because from extended experience with sodium peroxide, this jar was found to be tlie only container having a perfect seal. Twentyone other samples \rere collcctcd a n d scaled in the ordinary Mason jars. After staiiding in tlic laboratory for a b o ~ i tten months, twenty-six of the " Lightning" jars, upon opening, showed a slight pressure of gas which ignited with a strong blue flanic, burning from one-half to six inches in heiglit above thc. top of the jar. Upon covering and retesting, these jars ~voiildriignite for two or three successive times. Yone of the samples sc:iktl i l l tlic. Mason jars would so ignite. Two points arc. t o be noted liere, nninely, that the coal content very iiearly fillcd the jar aiid that the enclosure in the Putnam jar is practically that of a continuous glass scal, .ivhilc the Mason jar is quite different as to the security with which tlic gasket is held and, in addition, has a large metallic surface esposcd t o the transmission of gases. Another test pertains to thc enclosing of the air-dried samples of the same coal in Putn:iin jars for iiiore than eighteen months with the dry coal occupying about one-quarter of the jar, Upon opening, all of these jars showtl :L cry positivc, cvidcncc of the absorption of oxygen a s indicated b y tlic estinguishiiig of ;L lighted match. .\nalysis showed net' of lcss thati I.,? 1)cr cent. os!-gen and lcss than 2 per cent. of carbon tlioside. 'J'.wLP; Test.
So. ~.-I.oss IN CALORIFIC VALUE DURING
No.
1,ocality.
Size of coal.
I
Westvillc
1 3 inch xreenings
" ' I
2
Springfield
3
Herrin
'
3
3 .3
'
'(
coal from the seam, namely, the ox,idation of compounds in the coal. 'l'his is, perhaps, more properly designated under tlie mine of weathering. .idvantage has been taken of the f x t that i:i a number of mines, old pillars have been st,inding, and samples liavc. beeii procured from these, aiter properly cleaning the surface, and comparir,g t h e results wit11 sniiiples obtained a t the freshly worked faces of the mine. In 'I'ablc S o . 6 the results are given for such samples from pillars tweiity-t \YO and twciit y-scvcn years old. T h e pillar coal shohvs a loss in coinliarison with the fresh coal of approximately 2.5 per cent. In the sainc tablc are gil-en also the results for samples from another mine which have bccri subjrctcd to various conditions, including submerging for oiie year, :1nd the analysis of coal which has been exposed to tlic weather for one ?-car. T h e diffcrcncc is inappreciable as between the outer surface of tlie p i k :irid t1i:it of tlic interior. B . T . U . per Dropin heat lb. referred units com-
Test No. I 2
3 4
5 6 7 8 3 IO
Milt e r in I,
to ash. pared with water e n d initial sulphur-free. values.
Tielleville, Illinois Fresh face sample Pillar coal, 2 2 years exposure Equality, Illinois Fresh face saniple Pillar coal, 2 : years expowre JI'estvillc, Illinoi~ I inch screenings I M cek from mine 3 inch nut, I week from mine 11 inch screenings, submerged I week after mining, for I year From surface of 1 5 ton pile, I year ex posure From throughout I j ton pile, I year exposure Four neeks after mining
1.5188
14751
434
14627 11586 14588
14241
347
14264 14410
324 178
Six other weathering tests have been conducted on smaller samples by Mr. N. I>. Hamilton. fiach sample was subjected to different conditions, namely, subniergecl; exposed to the weather; exposed to a dry
103 3
THE DETERIORATION OF COAL.
atmosphere, a t a rather elevated temperature; and a duplicate of the latter with frequent drenchings with water. A charting of the results, which is more or less characteristic of all the tests, is given in Fig. I,
OAKWOOD
NUT
SAMPLED ONE
AND SLACK. DAY AFTER MINING.
1500C
3
2 t; 3 m z 0 u L
0
P
5 l400C 0
n oc Id P
5
em
-----
AT
8 5 " T O I Z Q " ~DRY.
-.- . AT 85% IZOT WETTED OFTEN
13000 1
I
2
3
4
5
6
7
8
9
10
TIMEOF EXPOSURE-MONTHS. FIG. I.
which is sufficiently clear to be self-explanatory. While the results of this series of tests are not conclusive, they point to the fact that submerged coal is without loss so far as oxidation processes are concerned; that exposure to a dry atmosphere is quite as conducive to the loss of heat values as exposure to weather and that, in general, these calorific losses are largely overestimated and probably, on an average, do not exceed 3 or 4 per cent. in amount, A continuation of these tests upon carload lots is now being made under conditions of outdoor exposure, housing in bins, and in the submerged conditions, with some accompanying experiments intended to develop, if possible, the conditions which result in spontaneous combustion. U N I V E R S I T Y O F ILLINIOS, UREANA, ILL.
