W . NIEHLS.
3 96
AN IXPROVED M E R C U R Y -
:b :
[>
I .698
2CsCl,RuCl,NO,zH,O 2RbCl,RuCl,NO,zH,O
1.692 :
76-,
c
(I A
o
021 A OOI
io1
A
100
:
c I. I
........... ........... ...........
0'1
5 8 . ) 45' 33', IS', 30'' 38-, 31',30" 46 , 12' 66 , 22', 30'' 6 j , ~j', 30"
i = 76 , I I ' i=76 , j o i '
7;
I : 1.242
2CSCI,KUC1,90.2FI,U. I I!*
132',, 45'" 6 2 ' , 13'
if A
I
Calculated
Sleasured.
30',
:
6 2 , 2 j ' , j9" 58'. 46', 6" p'-, 3.5' 3 s 5.3'9 23" 46 , 1 1 ' 66 , 30' 64 , g j ' , 37" I
3leasirred. 2 KbCl , K u C 1
76 31
C:iiculated.
s0 . 2 1 f
. jo', y)"* ...........
.
IS'
13j', A'* 117'.
30"
gS-. jo'
...........
39 , 32' 46') 6'
...........
63 , 33'
jr
,
?SI,
281'
........... ........... 58 , I j ' 3.3' 3 j 1 , 33" 40 37'q 9" 4j , 2 2 ' . 2 ' ' 6 j , 32' 62 , 321, Z I ' l 9
Both salts shav a perfect cleavage parallel to a and a poorer oiie parallel to c. T h e plaiie of the optical axes is the clinopiiiacoid ; the double refraction is strong, aiid the optical orientation such that cleavage plates parallel to a show in convergent polarized light an optical axis altnost iii tlie center of the field. This iiivestigatioii was i i i a t l e i n the mineralogical-petrographical laboratory of the Sheffield Scientific School, under the direction of Prof. S . L. Peiifield, to wlioiii the author's thaiiks are due. AN IMPROVED MERCURY THERMOMETER FOR
HIGH TEMPERATURES.' n> w
T
SIFHIS
H E ordinary mercury therinonieters give accurate values up to 250' C.
When the thennometer tube above tlie mercury
is filled with nitrogen under pressure, readings are possible up to 450' C. Early in I 893 I submitted to the Physikalisch-Technische Reichsanstalt, at Charlottenburg, Berlin, which, as is well known, tests the correctness of normal thernioiiieters, etc., iiiodels of high temperature thermometers which were capable of giving accurate readings up to 550' C. Since then iiiinor details of construction have been satisfactorily completed, aiid iii the
following, I will briefly describe tlie perfected iiistruiiieiit. 1Read before t h e Ciuciiiuati Section, April 16 1394
THERMOMETER FOR HIGH TEMPERATURES.
397
At the outset it was necessary to secure a variety of glass which does not soften below 600". For this purpose the borosilicate glass of Jena was chosen and has shown itself well adapted in all cases. T h e graduation is brought directly on the tube, and ranges either from IQO"to jjo" in siiigle degrees, or froiii 100" to 5 50' in intervals of fire degrees. T h e scale is black, for the sake of the greatest clearness, and the iiiethod of its preparation is as follows : T h e thernionieter tube is supplied with the requisite amount of mercury, and then completely filled with carbon dioxide under a pressure of twenty atmospheres. In this condition the tube is heated and graduated. T h e mercury is then removed, black enaiiiel is rubbed in tlie scale, and the tube is introduced into a muffle where tlie scale is brought out clearly in enamel. This treatment in the muffle has iiot only the advantage of yielding a permanent scale which resists strong acids, but it also brings about an artificial ' ' ageing " or seasoning " of the thermometer. I n other words, it decreases iri a marked degree, the tendency of a theriiioiiieter to give too high readings as time goes on. This is evident from tlie following experiiiiental data : Thernionieters graduated to 360', which showed ordinarily a rise of 8'-10°, gave, after this preliiiiiiiary treatment, when heated Those for ten hours to 34O0-3jOo an iiicrease of but 0.6"-0.8'. graduated to 400" showed, under the saiiie conditions, a rise of I . 5"-2'. In the case of thermometers graduated to 5 jo" the rise under the same conditions was 2"--3". After further heating for On the contrary, tlierniometell hours the rise was 0.4"-0.6'. ters graduated to j5oo, but not exposed to tlie ' ' seasoning " treatment, showed, after being heated for ten hours, a rise of 16"~ g ' ,arid after a further period of ten hours a rise of 4"-6", while further increase was naturally to be expected. A further iiiiprovenient of tlie high temperature thermometer is the coating on the back of the tube which greatly facilitates readings. This saiiie result has been secured in tlie construction of ordinary thermometers by introducing into the back of tlie tube a strip of enamelled glass. T h e difference in the coefficients of expansion renders this impossible in the case of the high teiiiperature theriiioiiieters. T h e strip of enamelled glass has been
398
THOMAS
s. G L A D D I N G .
ON
'rm
replaced, however, very satisfactorily 1)). a siniple coating of enamel which is fused upon the surface of the tube at the same tiine that the figures of the scale are produced. T h e enaiiiel on the rear of the tube, as well as that of the graduation, are totally unaffected after prolonged exposure to high teniperatures. A n extended use of these thernioriicters is to be expected riot only in laboratories, but in many branches of chemical industry , such as tar works, petroleum refineries. aiiilin works, etc. I would mention in this coiinectioii the great help I have experienced i n using Xahlke's ' . thread thernioiiieter " for obtaining accurate readings at high temperatures. This gives the proper correction for the error due to the projection of a part of the mercury column of the theriiioiiieter outside of the substance or confilled space. the teniperaturt. u l lvliich is being measured. 111 the case of Ioiig tliernioriieters and high teniperatures this error iiiay reach 30'. Nahlke's thermometer is hung alongside the projecting part of :I theriiionieter i n use, arid is so arranged as to give at oxice the reading for the riuiiiber of degrees to be added to the temperature indicated in order to correct the error mentioned.
ON THE ESTIMATION OF SULPHUR IN PYRITES.' BY
T
'rHOMA5
S
GLADDIXG
HERE are two recognized methods for the estimation of
sulphur in pyrites which, with various modifications, are chiefly used by coniniercial clieriiists at the present time. These are : First, the fusion of the ore with a mixture of sodium carbonate and potassium nitrate, solution in water, filtration from iron hydroxide, and precipitation as barium sulphate. Second, the solutioii of the pyrites ore in aqua regia, or in aqua regia and bromine, aiid subsequent precipitation as barium sulphate. T h e following investigation was undertaken to cleterniiiie the relative merits of these two methods and the proper modifications to be observed : A chemically pure potassiuni sulphate was examined for 1 Read
before the New York Secliotl. March 9 , xS94
