278

THE COLLIERY GUARDIAN.

February 7, 1913.

Table 1a.—Results Showing Percentage Lost by Coal when Heated at 104—107 degs. Cent, fob One Hour.

Particulars of method.

Coal Number.

Worker.

Grammes
of coal.

Weighed in

Heated in

2.	3.	;	4.	5.

in.

IV.

V.

VI.

VII.

VIII.

XII.

XIII.

XIV.

XV.

XVI.

1
1
1

1

1

1

1
1
1
1

1

1

1

1

Platinum crucible.

Porcelain crucible.

Porcelain crucible.

Porcelain crucible.

Platinum crucible.

Watch glasses.

Shallow stoppered weighing bottles.

Porcelain crucible, weighed covered.

Weighing bottle.

Porcelain crucible.

Berlin porcelain crucible oo.

Watch glasses.

Nickel boat weighed in tube.

Porcelain crucible with lid 40 mm. at
top.

Porcelain crucible with lid.

As officially described.

As officially described.

Wiesnegg oven.

Electrically-heated oven, 100—105 degs.

Electrically-heated oven, 100—105 degs.

Oven with air circulation at 105 degs.

Toluene oven.

Thermostat at 105 degs.

Toluene oven.

Toluene oven with air current.

Air bath with 2 thermometers, 105 degs.

Air bath with 2 thermometers, 105 degs.

Air bath with 2 thermometers, 105 degs.

V. Meyer toluene bath.

Air bath with current of dry air.

D’Arsonval oven with glycerine bath, with
Roux bi-metallic regulator 105 degs.

Oven at 105 degs.

Toluene bath.

2*80
2'92
2*86
3’05

3’13
2'87
2’92
3*11

2'75
3'15

mi2'97

3'22
2'72
3'06
3'24

3'16
2'90
2'95
3'19

2'96

2'861

2'78 >2'79
2'72 J
i>-92
2'72

9'50
9'76
9'58
10'25

9'99

9 86
9'76
10'06

9'63
9'59
1016 hop
10'16) 10 11

9'72
9'18
9'82
9'92
10'16

9'83
9'86
10'22

10'16

9'80)

9'79 >9*77

9'75}
9:92j9-9o

9'40

7'00

7'49

7'31

8'00

7'98

6:98

6'90

7*74

7'37	;

7'47	!

7‘54 ) „.kq

7'64) 7	i

6'52

6'66

7'34

7'46

7'79

7'17

7'34

7'52

7'30

7*191

7'07 > 7'13

7’13} j

7‘47 7 7.46 ?

7'45 ) ' 40

8'96 • t

5'10
5'53
5>5
605
5'98
5'86
5'83
6'08
5'77
5'38

5-9515'98
D vv j

5'88
5'28
6'04
6'24
6'19
5'67
5'95
6'42

5'86

6'00)
5'94 >6*00
6'00}
6'06 )
6'03 ) 6 05
5'15

6'90
7'30
7'26
7'68
7'44
7'14
7'21
7'56
7'09
7'38
?:S}7’64
7'14
6'56
7'24
7'32
7'34
7'03
7'28
7'47

7'20

7'05)

6'99 > 6'99

6'22}

6'78

Maximum..................................... 3'24

Minimum.................................... 2’72

Average...................................  2'96

10'25

9'48

9'84

8'00

6'52

7'33

6'42

5'10

5'84

7'63

6*22

7'20

7'10
7'80
8'04
8'01
8'16
7'43
7'48
7'66
7'31

7'56

7‘917 7*95
7'98) '

7'10
6'92
7'53
7'46
7'45

7'45

7'92

7'111
7'23 5- 7'13
7'05}

7 4$ ) 7*45
7'40 ) '

6'80

i	8'16

I	6'92

j	7'48

la. Standard American Method.

The following method for the determination of
moisture in coal is taken from a report of the committee
of the American Chemical Society on Coal Analysis
(W. A. Noyes, W. F. Hillebrand, C. B. Dudley), Journ.
Am. Chem. Soc. 1899, xxi., 1116-32.

One gramme of the coal is dried in an open porcelain
or platinum crucible at 104 to 107 degrees Cent, for one
hour, preferably in a double-walled bath containing
pure toluene, although any bath giving the necessary
temperature may be employed. Cool in a desiccator
and weigh covered. Longer heating is undesirable, as
oxidation and increase in weight occur. A higher
temperature is not advisable, although the results
obtained when using a xylene bath (138 degs. Cent.)
indicate that variations of several degrees in the
temperature of the bath, if sufficiently above the boiling
point of water, have no effect.

This method is entitled to serious respect as the
outcome of a considerable amount of work by the above
committee. It is probably very largely, but by no
means universally, used. This is shown by the fact
that several members of the present sub-committee
do not ordinarily use this method or any modification
of it.

We have indicated in the table the various arrange-
ments used by workers. This information we supplement
by a few more detailed notes.

I.	—The Wiesnegg oven is an inner porcelain vessel
heated by tube burners and contained in an outer cast
bronze vessel, between which and the porcelain the
products of combustion escape.

II.	—The electrically heated oven had triple walls, and
was heated by means of a nickel iron coil outside the
drying vessel. A thermometer, placed with the bulb on
a level with the vessels used to hold the coal, did not vary
day or night. It remained at 105 degs. Cent. The double-
walled gas-heated oven used by this worker for some of
his experiments did not vary in temperature by deg.
The supply of gas was regulated by a governor.

V.—The thermostat was heated by steam under such a
pressure as to secure a temperature of 105 degs. The
results shown are mean of closely agreeing duplicates.

VII.—Weighings corrected for errors of weights but

not reduced to vacuum.

sampled down from bulk.

over fresh H2SO4.

VIII.—Crucibles and closed bottles cooled in calcium
chloride desiccator.

X. Upper part of bath protected by flannel cover.
Crucibles placed on perforated shelf under which were
two other copper shelves, close but not in contact.

XII. Tube air bath described Journ. Soc. Chem. Ind.,
1896, xv., 417. Temperature inside bath within 1 deg. of
that registered by thermometer, as indicated by thermo
junctions wrapped around thermometer bulb and covered
with coal in the nickel boat respectively. Temperature
shown by thermometer constant to 1 deg.

An examination of the results obtained by drying for
one hour at a temperature of from 104 degs. to 107 degs.
shows that these conditions are by no means as strictly
defined as is to be desired and that to comply with them
is not easy. The observed variations for all the coals
are much greater than at first sight might have been
expected of so apparently simple a determination as
that of moisture. The differences between maximum

Duplicate estimations separately very risky proceeding.* We may here quote usefully
Bottles cooled in desiccator from the Report of Profs. Huybrechts and De Koninck,
who say of the former’s work by this method (XIV.):—

and minimum figures for each of the coals are set forth
below:—

1.	2.	3. ‘	4.	5.	6.

Per	Per	Per	Per	Per	Per

cent. cent. cent. cent. cent. cent.

0'52... 1'07... 1'48... 1'32... 1'46... 1'24
The averages being .. 2'97... 9'86... 7'33... 5'86... 7'21... 7'51

These figures represent variations of from 10 per cent,
to 22 per cent, of the amount of water present. From a
practical point of view, however, it may be contended
with some reason that it would be fairer to consider
these as determinaations of dry matter rather than of
water. In this case the order of the errors is reduced
to between 1 and 2 per cent. It should certainly be
remembered that it is the dry matter that signifies,
rather than the water associated with it. This considera-
tion does not affect the errors caused in ultimate
analysis by the presence of water in supposed dry coal.

A few sources of error may be considered. In the
first place, it cannot be contended that an ordinary
crucible, either of porcelain or platinum, is a vessel of
suitable shape for use in such a determination as that of
moisture in any substance; more particularly one as
liable to oxidation as coal, which should therefore be
dried as quickly as possible. The American committee,
in indicating that platinum crucibles, which are usually
of a tall form, give, on the whole, lower results than
porcelain, have hit on a weak point in the method
recommended by them.

This point is again brought out in the two series of
results of the worker II. who, in all cases, obtained
higher average results in porcelain than in platinum*
and higher individual results in all cases but one (No. 6),
this one difference being trifling. The worker V., who
used a platinum crucible, in only one case, obtained a
result (No. 3 : 0'04 per cent.) above the average.
It is, we think, clear that the aim in determinations of
this kind, should be to expose as large a surface of the
material to be dried as possible. A crucible is perhaps
the worst-shaped open vessel for this purpose.

Apart from the objection which we raise to the form
of crucibles used’ as drying vessels, we must point out
that coal is a very hygroscopic substance, and that to
weigh dry coal in an open or loosely-covered vessel is a

The process ... gave lower results than those furnished
by the first process examined (drying for 15 minutes in a
weighing bottle at 105 degs.). This was prophesied ... The
weight of desiccated coal in crucibles (fitted with their
lids) is less certain than the weight of these substances
in bottles ground in emery, for dry coal is very
hygroscopic.

The three crucibles containing the portions taken from
one sample were placed in the same desiccator. At the
time of weighing, the first was withdrawn, placed imme-
diately on the pan of the balance and fitted with its lid.
The weights of the second and third followed and were
taken as quickly as possible. Although the desiccator
was only open an instant and the weight was taken very
quickly, the absorption of a little moisture from the air
took place. This phenomenon was not very marked and
perhaps it would have escaped my attention if the second

* We allude later to the precautions to be observed in
handling coal samples in dry climates.

portion had not regularly shown (with two exceptions) a
loss of weight smaller than the first, the third a loss
smaller than the second (see Table 1a).

We have averaged all the results in Table 1a in which
the coal was dried in shallow stoppered weighing
bottles, watch glasses ground to fit, or a boat which was
weighed in well-fitting tubes. The figures are in every
case higher than those for the whole series tabulated
under la, as will be seen below :—

1.	2.	3.

3'08±0'04 ... 9‘96±0'08 ... 7'47±0'04

4.	5.	6.

6*00±0'U ... 7'42±0'06 ... 7'69±0'08

The greatest difference between individual results was
1.	2.	3.	4.	5.	6.

0'29 ... 0'63 ... 0'30 ... 1'04 ... 0'40 ... 0'53

It appears from these results, that the inferiority of
crucibles, more particularly of platinum crucibles, as
compared with vessels of glass with closely fitting
covers, is established.

The temperature of a substance placed in a oven is
not always easily ascertainable. More particularly is
this the case in an air oven heated by a gas burner or a.
series of burners. The bottom may be nearly red hot
and the top at a relatively low temperature. The
falling off of temperature between these positions is
affected by the air current which should pass through
the oven.

It is therefore a difficult matter to insure that the coal
placed in an oven, in some part of which a thermometer
indicates a temperature of 105 degs. or thereabouts, is
itself actually at that temperature. The effect of small
differences of temperature is probably negligible since
the American committee found that boiling xylene
(138 degs.) gave much the same results when used to
heat the drying bath as toluene. Members of this
present sub-committee (XII.) found that a coal which
lost 13'90 per cent, at 105 degs. in two identical
determinations in one hour in a current of dry nitrogen
(containing less than 0'5 per cent, of oxygen) lost as
much as 12'72 per cent, in the same time at only
63 degs., 13 34 per cent, at 79 degs. (after 2 hours 13'59
per cent., after 3 hours 13 69 per cent., after 4 hours
13'69 per cent., then after 1 hour at 105 degs. 13'95 per
cent.) 13'55 in a water oven, while the same portion used
for the experiments at 79 degs. and 105 degs. gave 13'78
per cent, at 130 degs., a gain due either to traces of
water or to oxygen in the nitrogen. The heating in
these experiments at 63 degs., 79 degs., 105 degs. and
130 degs. was performed in a bath in which the coal was
exposed to a constant stream of nitrogen (J.S.C.I., 1896,
XV., 417). It appears, therefore, that, so long as the
temperature is at least as high as 105 degs., no great
discrepancy due to this cause is probable, although it is
better to aim at the prescribed temperature of 104 degs.
to 107 degs., but, from these data, it is clear that
temperatures below 100 degs. give results which are
almost certain to be low, owing, probably, not to the
impossibility, but to slowness of the drying when the
greater part of the water has escaped.

(To be continued.}

Rumours of proposed new works are being circulated in
the Scunthorpe district. Surveying has been in progress at
Thealby, a village just outside Scunthorpe. It is also
stated that Messrs. Lysaght’s, of the Normanby Park
Steelworks, propose erecting three new furnaces.