Yale University. Dept. of Geology and Geophysics Wilmot Hyde Bradley.

The American journal of science online

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I have obtained some results which are worthy of record. In
some cases, as in the Warren, N. H. crystals, the interpretation
of the results may not be the correct one.

i. Molybdenite from Enterprise, near Kingston, Ontario,

In a quantity of material obtained from Mr. 0. W. Dickson
there was one doubly terminated crystal (fig. 1), about 8"°*
across by 2°*™ thick, the pyramidal faces of which were bright,
a little curved and almost free from striations, and the terminal
plane, which did not appear to be a cleavage, was bright and
showed few grooves.

The crystal was attached to a gangue of pyroxene, phlogopite
and pyrrhotite but projected so that it was possible to measure
the angles between the basal plane and two of the pyramidal
faces.

The faces did not yield single images and two separate
adjustments were made for each angle with different combina-
tions of lenses. The results, each in itself an average of four
or more measurings, were :

First angle. Second angle.

41°21i' 41° 28'

41 53 41 02

Average of all, 41° 26'.

This corresponds to a pyramid (2025) the angle for which cal-
culated to Brown's unit would be 41'' 23'.

♦Proc. Acad. Nat. Sci. PhUa., 1896, p. 210.

f BrOgger showed (Zeitsohr. f . Kryst. x, 507, 1885) that such markings
«onld be produced by pressure, and Magge attributed them (N. J. f. Min.
1898 i, 109) to translation along the plane 0001 perpendicular to the markings.



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360 A. J. Moees — CryatdlUzaiion of MohjbdeixiU.

2, Molybdenite from Aldfield, Quebec,

A specimen purchased from the Foote Mineral Co. showed
a barrel-shaped crystal (fig. 2), the basal plane 7X5°*% thickness
^rnm fjjQ cleavage surface was not crumpled and was free from
grooves and ridges but was pitted with little etch figures of
not very definite shape. The pyramidal planes were striated.

When adjusted on the two-circle goniometer by use of this
pitted cleavage surface, it was found that, at intervals of closely
60° of the vertical circle, zones were obtained which yielded
images of the collimator signal for two diflferent positions, both
positions corresponding to a bright illuminatiou of the entire
face. That is, the striations in this crystal are due to an oscilla-
tion between two forms and not to gliding or translation, this
being further proved by the absence of grooves and ridges on
the cleavage.

In each zone one of the two images corresponded to o
approximately 90°. The crystal was therefore readjusted until
these were exactly 90° and the results for the second image
thereafter in four zones were :

p

0° 77°20' Dull image

59^41' 77 21 Single image

120 09 77 10 Brighter of two

180 10 77 22 « " «

Average p= 7 7° 18'.

The variation of both (f> and p are not too great to be attrib-
uted to the blurred signals. For the pyramid f202l) observed
by Brown at Frankford, Pa., the corresponding calculated
an^le is 77° 13'.

That is, the crystal consists of a predominant pyramid (205l)
with striated faces, and these strise are due to an oscillation
between this form and the prism*.

S, Molybdenite from Cape Breton,

Among a number of small crystals of molybdenite in the
Egleston Museum labelled Cape Breton, one small crystal 4°""
broad by 1""" thick showed five faces of a pyramid, two of
which were unusually bright and intersected m a sharp edge.
Placed with this edge vertical in the No. 2 Fuess goniometer,
each face yielded a single vertically distorted image and permitted
a rather close reading. The interf acial angle obtained was 58^
28^', which corre8)>onds to an angle with the cleavage of 77^
29'. The calculated angle for (2021) is 77^ 13'.

* The faces of such crystals are slightly curved and the oryatab taper, pn-
venting an exact application of a hand goniometer. It is probable that the
angle cp=72° obtained by Hidden, (this Journal, xxxii, 210, 1886) on Benfrew
molybdenite in this way is due to an osciUatory combinatioin.



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A. J. Moses — CryaiaUization of Molybdenite. 361

i. Molybdenite from Okanogan Co,, Washington. '
Messrs. Geo. L. English & Co. permitted me to examine over
one hundred crystals from this locality. Many of these sug-
gested a pyramid approximately the (2025) found upon the
crystal from the Enterprise Mine, but the crystals were bent
and the faces bruised and rounded. Etch figures ^ to 1°"
across and six-sided in cross section were observed and upon
one crystal in which they were unusually distinct their parallel-
ism to the hexagonal outline of the crystal was shown by the
cross hairs of the microscope. This particular crystal also
showed three systems of fine lines parculel to the edges of the
cleavage in addition to a few coarse grooves perpendicular to
these edges.
The best measurements were obtained from a crystal (fig. 3)




which distinctly showed two pyramids, the brighter being the
flatter form but the steeper form being more developed. The
crystal formed one of a group and only two zones could be
adjusted for measurement. The images were multiple but the
groups were small and the angles witn the cleavage were :

Zonel. 30° 17' and 41° 46'

" 2. 29 32 Blurred



Average 29° 64' 41° 46

The neai-est simple indices are (10l4) (28'^ 51') and (2025)
4r 23'. If 41 "^ 46^ be taken as the angle of the unit pyi-amid,
the pyramid (10l4) would have an angle of 29° 10'.

A crystal, bent like that figured by Knop so that the ridges
divided the cleavage into three areas not in the same plane,
yielded an angle of 7^° 59' between a pyramidal plane and the
adjacent portion of the cleavage.
For (2021) the angle 77° 13' has been calculated.

5. Molybdenite from the Tilly Foster Iron Mine, JBrewsters^ N. Y,

Mr. F. V. Cruser presented the Egleston Museum with some

specimens of molybdenite found by him at the mine. They

occur in a cleavable calcite associated with small bright crys-



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362 A. J. Mose% — Crystallization of Molybdenite.

tals of green amphibole. On one crystal showing four faces
of a pyramid two adjacent faces intersected in an edge which
permitted careful adjustment on the Fuess goniometer. Each
yielded a bright image of the signal which was only slightly
distorted horizontally. The five readings of each face varied
with respect to the mean^ to the nearest half minute as follows;



First.


Second


-Hi


+ 0i-


+ 4i


-6


+ H


-8.


+ 6i


+ 6;


- H


+ 8-



The angle obtained was 54° 08', which corresponds to an
angle with the cleavage of 65° 31'. The angle for (lOll) on
the Frankford, Pa., crystals is 65° 35'.

6. Molybdenite Jrom Warren, Ni H.

In an old suite of molybdenite specimens in the Egleston
Museum 1 found a number of small doubly terminated crys-
tals three of which gave with the hand goniometer for all
faces an angle with the cleavage between 54° and 55°. The
pyramidal faces were striated and most of them curved and
the cleavage was curved.

One crystal (fig. 4) showing twelve pyramidal planes was
roughly oriented on the two-circle goniometer by the bent
cleavage. Three faint signals were obtained with ^ respec-
tively 60°, 120° and 240°, which were approximately p = 90°.
The crystal was then readjusted until these signals were accu-
rately p = 90°.

The results were analogous to those obtained with the Aid-
field crystal, that is images of the collimator signal were
obtained for two different positions, each of which corre-
sponded to a general illumination of the surface. In this case,
however, both corresponded to oblique angles (pyramids). The
results were






9




?





55° 15'


Two images


64° 36'


60


54 30


Bright image


64 58


119 06'


. - - _






180 24


Blur






240 20


54 25


Blurred image


64 18



Average 64° 43' 64° 27'

Phe simplest interpretation of these angles is that they corre-
pond to (2023) and (lOll), for which the corresponding calcu-



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A. e/l Moses — Crystallization of Molybdenite, 863

lated angles are 55*^ 45' and 65° 35^ Bdatively they are
fairly close to ealealated angles, for a unit angle of 64° 27'
would require for (2023) an angle of 54° 21'. It is not
unreasonable to suppose an error in orientation or in the read-
ing of the faint prismatic signals which would diminish both
angles about the same amount.

The conclusion, therefore, is a dominant pyramid (2023)
with striations due to an oscillation between this and (lOll) ;
the prism (lOlO) present as a slightly developed modification.

7. The Knop and Hdmes Measurements.

The crystals from Auerbach, Hesse, examined by Knop,* were
parallel plates often with curved lamellae. No regular twin
striations but frequent wrinkling which appeared to be perpen-
dicular to the sides of the hexagon producing approximations
to rhombic thirds of faces. Measurements did not give any
constant angles between these ' thirds,' which were evidently
results of bending or wrinkling.

Although, as might be expected, these bent crystals gave no
constant angles,t it is noteworthy that the averages both of the
angles with the cleavage and the angles between adjacent faces »
closely approach those of the unit pyramid.



Adjacent faces.


Faces with cleavage.


60° 07'


71^0'


56 49


69 04


56 37


57 20



Average 64° 31' 66° 48'

The Frankford, Pa., unit pyramid (lOll) has angles respec-
tively 54^ 10' and 65*^ 35^

With respect to the crystals from Greenland, Homes states :
"I have measured the crystals from Narksak and found the pyra-
mid J 23° 45', 140° 67'.'^^: Kenngott reexamined§ the crystals
and accepted the proof of their hexagonal form but pronounced
the pyramid dubious, attributing it to the slipping of curved
prisms and to tapering, but states, "one small crystal only
showed a fairly distinct acute hexagonal pyramid."

Hintzel gives these angles as jpc =70° 28^' and pp =56° 15'.
There appears to have been a slight error here, as for pp =
56° 15', w= 70° 31i'. This corresponds to (5054), for which
the calculated angle is 70° 03'.

* Sammarized from Neues Jahrb. f. Min., 1848, p. 43.

! Obtained by attaching mica to the faces.
Uebereicht DarsteU. des Mohsischen Min. Syst., 1847, p. 115.
gMin. FoTflchnngen, 1856. p. 104. | Mineralogie, vol. i, p. 104.



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864 A. J. Moses — Crystallization of Mol/yhdeniie.

Summary of Molybdenite Measurements.

Assuming the unit of Brown, viz., a pyramid o making an
angle co with the cleavage equal 65° 35' from which c =1'908
is calculated, the observations may be summed up as follows :
the angles with the cleavage being given.

Basal pinacoidy c (0001). Not observed except possibly on

Enterprise, Ont. crystal.
Prisniy m(lOlO). Frankford, Pa., sometimes prominent, Aid-
field, Quebec, as part of striations ; Warren, N. H., traces.
Pyramid, q{ZOl\). Calculated angle 81** 24'.

Observed at Frankford, Pa. Measured angle 81° 31'.
Pyramid, p (202l). Calculated angle 77° 13'.

Frankford, Pa. 77° 16'

Aid field, Quebec 77 18

Cape Breton 77 29

^ Okanogan Co., Washington 76 59
Pyramid, r(50§4). Calculated angle 70° 03'.

Observed at Narksak, Greenland. Measured angle 70° 31^'.
Pyramid, o (1010). Unit angle, Frankford, Pa., 66° 35'.
C Tilly Foster Mine .... 65° 29'

Measured angles ^ Auerbach, Hesse 65 48

(Warren, N. H 64 27

Pyramid^ t (20§3). Calculated angle 65° 45'.
Tlie Warren, N. H., angles for this, 54° 43', and unit are rela-
tively close for these indices but low for the Brown unit
Pyramid, «(2026). Calculated angle 41° 23'.

Measured angles \ Enterprise, Ontario 41 ° 26'

Measured angles ^ Qkanogan Co., Washington. 41 46

Pyramid, u{\0l4). Calculated angle 28° 51'.

On Okanogan Co., Wash., the angle 29° 54' was obtained,
which was near these indices for 20§5 = 41° 46'.
Columbia University, January, 1904.



Measured angles



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Gooch and McClenahan — Tyfical Hydrous Chlorides. 365



Abt. XXXIII. — The Behavio7' of Typical Hydrous Chlorides
when heated in Hydrogen Chlorine ; by F. A. Gooch and
F. M. McClenahan.

(CootribotioDS from the Kent Chemical Laboratory of Yal<s Uniyersity — CXXVI.)

The Iialogen salts of the metals are convertible by the action
of water to oxy-salts, hydroxides, or oxides with varying
dep^es of readiness. In order that water may act hydrolyti-
cally upon barium chloride, for example, with liberation of
hydrogen chloride and substitution of oxygen for chlorine, the
temperature of the system must approach low redness, while
magnesium chloride is attacked at a much lower temperature,
and aluminum chloride is extremely sensitive to the metatheti-
cal action of water. These reactions follow the indications of
the heat moduli of the transformations. To eflfect the meta-
thesis between barium chloride and water, with formation of
barium hydroxide and hydrogen chloride, a very considerable
accession of energy from without the system is needed; the
similar reaction between magnesium chloride and water requires
less reinforcement from the outside ; while the reaction between
anhydrous aluminum chloride and water takes place easily.
When a hydrous chloride is heated to the temperature of decom-
position, the products will be the anhydrous chloride and water,
or hydrogen chloride and an oxychloride, oxide or hydroxide,
according to the nature of the particular chloride under experi-
mentation. Hydrous barium chloride, BaCl,*2H,0, parts with
all its water and becomes anhydrous at 100^ C; the hydrous
magnesium chloride, MgCl,'6H,0 may lose a large part of its
water at temperatures considerably above 100° without apprecia-
able loss of chlorine, but exchanges chlorine for oxygen with
formation of hydrogen chloride at higher temperatures ; while
hydrous aluminum chloride, AlCl/611,0, loses water only with
simultaneous formation of hydrogen chloride and exchange of
chlorine for oxygen at 100°, and at temperatures at whicn all
water is removed is converted to ahiminium oxide.

It is obvious that in those cases in which hydrolytic decom-
position takes place at temperatures below those at which the
tendency to reversal ceases, the rate of decomposition must be
affected by the concentrations of the active products of decom-
position. So it is natural to expect that an increase in the
concentration of hydrogen chloride in the system will serve to
restrain hydrolytic action and decomposition of the chlorides
at temperatures of incipient hydrolysis. Dumas* tried to take
advantage of this principle in the preparation of anhydrous
magnesium chloride, free from oxide, by prolonged drying of
♦ Ann. Chim. (3), Iv, 137.

Am. Jqor. Sol— Fourth Series, Vol. XVII, No. 101.— May, 1904.
25



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366 Ooocli and McClenahan — Typical' Hydrous Chlorides.

the hydrous chloride in an atmosphere of hydrogen chloride,
but at the temperature of incipient redness at which Dumas
worked the reversal of the hydrolytic eflfect is slow and difficult.

In the case of a hydrous chloride, like barium chloride,
which shows no tendency to underffp hydrolytic decomposition
at temperatures at which the water as completely removed, there
seems to be no reason for anticipating any marked effect upon
the progress of the dehydration when hydrogen chloride is made
the surrounding atmosphere instead of air. With a hydrous
chloride which evolves hydrogen chloride at the temperature
of dehydration and forms an oxychloride, oxide or hydroxide
the case is different. In such a case the effect of enormously
increasing the concentration of hydrogen chloride in the system
at the temperatures of incipient hydrolysis will naturally be to
restrain the hydrolysis; but whether the result will be the
formation of a chloride of lower content of water or an
increased stability of the hydrous chloride for some range of
temperature will turn upon the aflSnity of the anhydrous chlor-
ide for water.

In the process of dehydrating hydrous aluminum chloride,
for example, an increase in the concentration of hydrogen chlor-
ide in the system will tend to retard the exchange of hydroxyl
for chlorine at the temperature of incipient hydrolysis; but
whether the result of such retardation will be the formation of
the anhydrous chloride or simply an extension of the range
of temperature for which the original hydrous chloride is stable
is not immediately obvious, though the high degree of attrac-
tion existing between anhydrous aluminum chloride and water,
as indicated in the large heat of hydration of that salt, would
seem to suggest the latter alternative.

In the work of which an account follows the effect of sub
stituting an atmosphere of hydrogen chloride for ordinary air in
experiments upon the dehydration of typical hydrous chlorides
was studied. Barium chloride as the representative of salts
which lose water without other decomposition, magnesium
chloride which suffers some loss of chlorine when fully dehy-
drated, and aluminum chloride which loses all its chlorine
when similarly dehydrated, were the hydrous chlorides taken
for these experiments.

In these experiments two combustion tubes of large size set
horizontally side by side in a tubulated paraffine bath served
as heating chambers. Each tube was fitted with a thermometer
and connected through a drying bulb and column with an aspi-
rator. Portions of the hydrous chloride to be treated were
weighed into porcelain boats. One of these boats was inserted
in each tube about midway in the bath (heated to a regulated
temperature) and immediately below the bulb of the thermom-



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Gtmek oofid McClenahan — Typical Hydrous Chlorides, 367

eter, so that the temperatnre of the material in the boat might
be indicated by the thermometer as nearly as possible. Through
one tube wasdrawn slowly a current of air purified by caustic
potash and sulphuric acid, and through the other was sent a
slow current of hydrogen chloride, generated in a Kipp gen-
erator by the action of sulphuric acid upon sublimed ammonium
I chloride in lumps. At the expiration of a definite period, the
boat was withdrawn, placed in a desiccator and weighed after
a suitable interval for cooling. The residue in the boat was
dissolved in water, acidulated with nitric acid and the chlorine
in it was precipitated by silver nitrate, the silver chloride being
weighed on asbestos. Thus it was possible to determine directly
the loss of water and chlorine from individual portions of the
salt under experimentation during definite intervals and at
fixed temperatures, both in an atmosphere of hydrogen chloride
and in air, and to find for each individual portion under experi-
ment what proportion of the total loss was hydrogen chloride
and what was water. The tabular statements and the diagrams
show the course of decomposition of the various salts for the
temperatures indicated.

Hydrous Barium Chloride,

For the experiments with barium chloride a well-crystallized
specimen showing by analysis a normal content of chlorine was
taken. During the process of dehydration at temperatures
ranging as high as 100°, at which point all water was expelled,
there IS no evidence of loss of chlorine, and the course of
dehydration, as would be anticipated, appears t-o be wholly
uninfluenced by the presence of hydrogen chloride.

The slight increase in the chlorine generally found in the
salt after exposure to the atmosphere of hydrogen chloride may
be properly attributed to occlusion or adsorption of hydrogen
chloride. The data of individual experiments are gathered in
Table I, p. 368, and the general course of action is followed
in the diagram.

Hydrous Magnesium Chloride.

Similar experiments, the data of which are given in Table
II, were made with hydrous magnesium chloride dried «V? vacuo
over sulphuric acid and of nearly ideal constitution.

So far as these results go, it appears that the loss of chlorine
during the process of dehydration of the hydrous magnesium
chloride, MgCl,'6n,0, is generally small until a temperature
approximating 200° is reached; that at temperatures between
100° and 130° hydrogen chloride generally restmins dehydra-
tion, while above that temperature dehydration progresses more



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368 Oooch and McClenahan — Typical Hydrotta Chlorides.

Table I.

Ba 56-24

CL 29-02

2H.O 14-74



100-00



Atmos-
phere.



j Air
(HCl
J Air
(HCI
jAir
] HCl
j Air
(HCl
\ Air
]HC1



Weigrhts
taken,
grm.



Loss on
heating.



0-3335
0-2952
0-3609
0-3004
0-2919
0-3362

0-4161
0-29V2
0-4904
0-4272



grm.

0-OI89|
0-0206I
00262,
0-02131
I0-02O6!
0-0243!



Per
cent.



Chlorine in residue.



grm.



I



5-67|00969 29-06
6-94 0-0866 2934



Per Varla-
oent. itionfrom
! theory.



+ 0-04
+ 0-32
— 0-06



Water

evolTed.

Per

cent.



Time,
hrs.



Temper-
ature.



7 I



7-26 0-1045|28-96
7-09 00875 29-13 -f 0-11
7-06 00848 29 051 -f 0-03
7-23 0-098ll29-l8|-h0*16
00557 13-38 0-1207 2901 — 0-ni
0-0389 13-09 00894 30-08 +106
0-071 1 14-49 0-142329-02 000
0-0630! 1 4-75 0-1236 28 93 —0 09



567

7-27

7-20

7-21

7-09

7-39

13-37

14-18

14-50

14-64



its,

is
i)
i)
i)
i\
i}



60"

60°

90'

100°




«^.



to*



7"'



8<



f«*



/•i



rapidlj^ in the presence of hydrogen chloride. Hydrogen chlor-
ide appeal's to influence in no very marked and regular way
the loss of the first third of the water.



Table II.

Mg 1 1-98

CI, 3487

6H.O 53 16



10000



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Oooch and McClenahwn — Typical Hydr(ms Chloridet. 369



Atmos-
phere.



(Air
'JHCl

2 (Air

-(Air
HHCl
.(Air
*"|HC1
.4 Air
*'|HC1
J Air

► (Air
' I HCl



8-



( Air



HCl



»J Air
'" I HCl



11



( Air
I HCl



12 3 Air
'^ I HCl

Air

HCl

Air

HCl

Air

HCl

Air

HCl



H
■•I
H



Weight

t aken .

flrrm.



0-5004
0-4830
0-5139
0-4310
0-7281
0-6093
0-7193
0-6183
0-2854
0-2453
5036
0-4591
0-6679
0-5012
0-5893
0-5145



Lots on
heating.



grm.

0093
0-0046

00181
0-OUO

0-0387
0-0240



Chlorine in residue.



Per
cent.

1-85|
1-06
3-52!
2-55
5-31
3-93
0-1026 14-26
0-0900i 14-55
0-0497117-41
0-0405 16-51
0-0927!l8-41
0-0799| 17-40
0-16ir24-12
0-0908 18-11
0-1404I23-82
0-1018119-78



grm.



1-



0-5012 0-13l4'26-21
0-4542JO-094420-78
0-4249!o-1043'24-55|
0-4l76,0-ll04!26-44
0-489l|o-15lll30-89i
0-366210-1093 29-85



0-1781
0-1503



0-2488
0-2155
0-9913
0-8486
01 755
0-1599
0-2327
0-1750
0-2055
0-1801
01678
0-1586
01480
0-1461

0-1721
0-1283



0-3583
0-3800
0-3918 0-0716! 18-27



0-0452112-61

0-0503 15-24

L



0-3964 0-081 1|20-46
0-3618!oi057 29-2r
0-3695 0-1225 33-15'
0-3380 0-1079'32-40
0-3209 0-1426 44-44
0-2728;0115642-38'
0-8583|o-167l!46-64,



0J240
0-1151
0-1359
01376
0-1240
0-1278
0-1091
0-1143
0-0900
0-1179



Per
cent.



34
34
34
84
34
34
34"
34
34
35
33
34
34
34
35
35



Varia- I
tionfrom!
theory.



Water

evolved.

Per

cent.



Time,
hrs.



— -21
-00



I 1-85

I 1-06

I 3-8

I 2-65



u



- -35

- -02

- -08

- -27

- -02

- 04

- -03
+ -04

-00

+ -13

-1-39



52

85
79.
60
85
88
84
91

87
00

48

92|+ -05
851— -02
991+ -12
19|+ -32
04:4- -17



17-38 i
16-23 J



13-90
4-51
!l
16
18-39
;i7-36
i24-09
18-15
i23-82
19-91
1-24-78
20-83
i24-53
26-56
131-2
;3002



\



34-61|— -16

34-88|+ -01

34-69|- -18

34-71 - -16

34-27|— -60

34-59'— -28
32-76| — 2-11

35-6il+ -75

33-20|-l-67
32-90. — 1-97



12-45 I

15-25 I

18-09 I

20-30

28-59 I

32-86

30-13

45-21

40-66

44-61



Tern*
pera*
ture.



I



50

60

70

90

100

105

1110

|115

|l20

|l25

il30



i 1156

i 165

i 195

\ 205

i 215



Hydrous Aluminum Chloride,

Pure hydrous aluminum chloride, A1C1,-6H,0, was made by
dissolving the C. P. hydrous chloride of the laboratory in the
least possible amount of aqueous hydrochloric 'acid, filtering
the solution through asbestos, and saturating the clear solution
with gaseous hydrogen chloride. The crystallized chloride
thus obtained was collected on asbestos in a perforated cone,



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370 Oooch and McClenahan — Typical Uydrous Chlorides.

washed with concentrated hydrochloric acid, sucked as dry as
possible by the pump, and exposed seventy -two hours in a desic-
cator containing quicklime, to absorb free hydrogen chloride,



Online LibraryYale University. Dept. of Geology and Geophysics Wilmot Hyde BradleyThe American journal of science → online text (page 39 of 53)