GENERAL, PHYSICAL AND INORGANIC.
1030
TABLE3 CHAXGG ~
OF T H E MOL
NUMBERSW I T H
THE ClJBE-ROOT OF THE? CONCENTRA-
TION.
Substances.
K.
MC1 and MBr, . . . . . . . . 0.292 NaC10, and NaBrO,, . , o,334
Conc.
0.005
{:E.
1,9521,9371,9251.887 1.8641.837 1.804 1.950 1.937 1 . 9 2 1 1.893 1.865 1.829 1.768
I I
0.01
0.02
0.05
0.1
0,5
10.2
Obs' ' . I.go2 1.883 r . 8 5 2 ' Calc. . . . . . I ,909I .8;7 I , 8 4 j . . . . . . KC10, and KBrO,, , , , o,418 Obs. l.919 1.8941.853 " . ' ' ' Calc. . 1.910 I ,887 1.8461.806 . . . . . .. lobs. 1.940 1.915 1.886 1.835 1.769 . . NaIO, and KIO,. . . . . . 0.45 jCalc. 1.9231.903 1.8781.834I .791 . . . . . . 2 . 8 5 7 2.798 2.723 2 . 5 8 0 2.466 2.339 2.135 Na,SO, and K,SO,. . . . . I . In Calc. (Ibs.2.8122.763 2 . 7 0 2 2.595 2.490 2.356 2.127 BaCI,. . . . . . . . . . . . . . . . 1.00 Obs. 2.j97 2.756 2.709 2.637 2 . 5 7 5 2.515 . . . Calc. 2.829 2 . 7 8 5 2.729 2 . 6 3 2 2.536 2.415 . . . Qbs. 2.779 2,.700 2.607 2,4482.298 2.136 1.854 Pb(NO,),. . . . . . . . . . . . . Calc. 2.749 2.6842.6022.459 2.318 2 . 1 4 0 I ,833 Obs. 1.6941.6181.536 1.4201.3241.2231.084 ~ ~ g S . 0. ., . . . . . . . . . . . . 1.60 Calc. 1.726 1.655 1 . 5 6 6 1.4111,2581.064 . . . Obs. 1.6161.545 1.455 1.318 . . . . . . . cuso,.. . . . . . . . . . . . . . . calc. 1.6751.592 1.485I ,301 . . . . . . . ,
'
'
'
'
'
'
'
'
'
'
i
differences not exceeding per cent. in the case of the chlorates and bromates. I n the case of the iodates aad the tri-ionic salts, however, the differences a t concentrations up to 0.1 normal frequently reach I per cent., but do not much exceed this. The bibivalent salts show deviations of several per cent., so that the principle can not be said to hold even approximately for them. Attention may also be called to the fact that (since K = -ddi/dC'/a) the value of the constarit K furnishes an obvious measure of the relative rates a t which the mol numbers of the various substances decrease with the increasing concentration. The regularities that exist will readily be seen by an examination of the values of K given in the table. BOSTOS,
June, 1910.
SILVER NITRATE FORMED BY THE ACTION OF NITRIC ACID ON SILVER SULPHIDE. BY HIPPOLYTE GRUENER.
Received May 30,
I~IO.
The statements which I have found concerning the products of the action of nitric acid on silver sulphide are incomplete and contradictory. The proportions of nitrate and sulphate formed vary widely with the conditions applied. Highly concentrated acid results in complete conversion to sulphate, while with the less concentrated acid there is formed a large percentage of nitrate. Besides concentration, temperature of the acid and time of action are influential. In the experiments summarized in Table I, the precipitated sulphide
103I
ACTION OF NITRIC ACID ON SILvER SULPHIDE.
( 0 . 2 g.) was treated with nitric acid (usually 15 g. of the pure acid) diluted to the proper concentration. The mixture was heated, or allowed to stand a t the ordinary temperature. When the action had taken p1ace;hot water was added to dissolve the nitrate and sulphate, the solution filtered from the sulphur and unchanged sulphide, and repeatedly evaporated to dryness. The amount of silver found in the residue determined the amount of sulphide dissolved. The nitrate formed was determined by the method of Gcoch and Gruener.' The results are shown in Table I, which indicates the proportions of sulphide dissolved, and also the percentage of nitrate formed a t different concentrations, a, with boiling acid, and b with cold acid.
TABLEI. a . Acid boiling.
b . Acid cold.
_ p A -
Conc of "Os. Per cent
NO.of
expt.
I.... z.... 3.... 4.... 5...' 6.... 7....
94 71
65 55 45 35 25
a,...
20
9....
I5
..
IO
IO.,
I I . . . . 12.
...
13 . . . . 1 4 . .. .
7.5 5 2.5 1.25
_ c
Time of action.
50 min. 5 min.
....
min. 3 min. 3 min. 5 min. until action was complete until action was complete until action was complete 15 min. 30 min. 4 hours 20 hours IO
Per cent. of Per cent. possible AglS nitrnte Timeof dissolved. formed. action.
98.6 99.9
o 3.6
Per cent. of possible nitrate dissolved. formed.
Per cent. AgnS
99.4 98.8 98.9
35.2 57.9 71.9 87.8 94.7
6 days I8 hours 4 days 4 days 4days 6days 6 days I I days
98.9
90.9
11
days
98.8
97.0
97.2
90.7
11
days
98.3
92.7
99.0 96.4 75.0 86.0
..
7 mos.
98.8
88.9 74.8
7mos.
98.8
7mos. 7mos.
89.0 7.3
92.3 84.4 75.8
.. .
100
98.4
..
60.4
IO0
0
95.0 99.4 99.5 99.5 99.7 99.3 98.6
7.2 22.6 29.0 58.4 77.0 91.5 95.9
0
The complete conversion of the sulphide to sulphate by the strongest acid used suggests the other extreme, namely, complete conversion t o nitrate. But the maximum formation of nitrate is found a t about 20 per cent. acid, and with greater dilution the amount of nitrate is found to diminish. The advantage of the cold acid from the standpoint of the nitrate is apparent, for the average yield when the action takes place at ordinary temperature is about IO per cent. greater than when the acid is heated. The time of contact of the reacting substances is important. When the sulphur liberated by the first action is promptly removed, i. e., by dilution and filtration, the percentage of nitrate is conspicuously greater than when longer contact is allowed. When the time of contact is less,
Am. J . Sci., 44, 117.
1032
GZNERAL, PHYSICAL AND INORGANIC.
ened to increase the amount of nitrate, there is also a diminution of the amount of sulphide dissolved. These points are shown in Table 11. 'r.ZBLE
HNO,
=
11.
.4g,S
7 1 per cent.
Acid boilinc of expt.
Time of action.
NO.
21..
, ,
,--
Per cent. P e r cent. AglS nitrate NO. of dissolved. formed. expt.
. . . . Heated just
to boiling 2 2 . . , . ,. . . 15 sec. 2 3 . . . . . . . . 30 sec. 2 4 . . . , . . . . I min. 2 5 . . , , ,... 5 min. 2 6 . . .. ... . 70 min.
62
39 5
31
97.5 96.6 91.4 99.7
37.5 21.1 8.4 3.6
32
I00
1.1
33 34 35 36
--
= aag.
Acid cold.
Timeof action. I
hour
3.5 hrs. 9 hours 18 hours 42 hours 66 hours
---
Percent. AgsS dissolved.
Per cent. nitrate formed.
37~0
32.8
53.6 85.2 95 99.7 99.8
20.8 12.9 7
2
0 8
0.3
Summary. Nitric acid, when of concentration above 5 per cent., dissolves precipitated silver sulphide rapidly. Very strong acid yields silver sulphate alone, while acid of lower concentration forms some nitrate in proportion to its dilution. 2-15 per cent. acid yields the maximum, about 95 per cent. nitrate, greater dilution again resulting in a smaller percentage. Heating the acid, or prolonging its time of action is unfavorable to the formation of nitrate. CHEMICAL L A B O R A T O R Y OF h D E L B E R T C O L L E G E .
CLEVELAND.
GRAHAMITE, A SOLID NATIVE BITUMEN. RP CLIFFORD RICHARDSON. Received June 24. 1910.
Grahamite is a solid native bitumen, the type of which was first found in Ritchie County, West Virginia, in the early sixties of the last century. It was named for the Messrs. Graham, who were interested in the commercial development of the deposit, by Henry Wurtz. The early literature of the subject' is largely devoted to the origin of the material and to its relations to coal, asphalt and albertite, as the latter occurs in Nova Scotia.2 It is largely controversial, which is not surprising in view of the fact that there had been little opportunity up to that time of studying and differentiating the native bitumens. I n 1890 Prof. Wm. P Blake, who had been interesting himself in the solid native bitumen found in such large amounts in veins in Utah and J. P. Leslie, Proc. Am. Phil. SOC.,9, 183 (1863). Henry Wurtz, AWL.J . Sci., -4.A . A . S., 18, 124 (1869); ,4m. Gas Light J . , 11, 98. S. F. Peckham, Am. Gus Light I,, 11, 164 (1869). 1 %'. M. Fontaine, Am. J . Sci., [3] 6, 409 (1873). J. P. Kimball, Am. J . Sci., [ 3 ] 1 2 , 277 (1876). Wetherill, Tvulzs. Am. Phil. Soc., 1852, 353. [ z ] 42, 420 (1865); Proc.
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