T H E SPECIFIC GRST'ITY -4ND PERCENTAGE S T R E S G T H O F SELENIC ACID BY JI. E. DIEMER AND VICTOR LENHER
It has been very desirable in making certain studies with selenic acid t o have the density and percentage strength data for various concentrations of the pure acid. The only available table is t h a t prepared by Cameron and Macallenl in their studies on selenic acid. The observations which they have made have been corroborated b y us, and are excellent for the range of concentration through which they worked. Their figures are from 99.73 percent t o 73.43. For acid more dilute than 73.43 percent, no data are available. IT-e have therefore deemed it advisable t o study the more dilute solutions, as well as the stronger acid. Preparation of Selenie Acid The starting material was fused stick selenium bought on the open market. This selenium was powdered, and treated with nitric acid diluted with an equal quantity of water. The resulting solution was evaporated to dryness t o expel the nitric acid. the selenium dioxide taken up in water and the insoluble matter always found in commercial selenium filtered off. The sulphur was removed by adding barium hydroxide t o the dilute aqueous solution of the dioxide until further addition failed t o produce a permanent precipitate, The barium sulphate was removed by filtration, and the solution evaporated t o dryness. The dioxide was resublimed until white. Two methods for the preparation of the selenic acid from this dioxide were used. In the first method diluted silver nitrate solution was treated with a dilute solution of selenium dioxide in water, and the resulting insoluble silver selenite washed free from all soluble compounds. The silver selenite l
Chem. S e n s . 59, 2 j 9 (1889)
506
M . E . Diemer and Victor Lenher
was suspended in water and treated with bromine water, when silver bromide and selenic acid were produced. The dilute selenic acid after filtration from the silver bromide, was concentrated by boiling under diminished pressure. A pressure of 30 m m and a temperature of 100 degrees completely removes the excess of bromine and any nitric acid. The final traces of selenous acid were removed by dilution and treatment with hydrogen sulphide. Alfter filtering off the small amount of selenium precipitated, the excess of hydrogen sulphide was removed and the acid concentrated by heating under diminished pressure. The fina,l concentration was made a t a temperature of 185' and a pressure of I O mni, solid potassium hydroxide being placed in the condenser t o facilitate the dehydration. Careful tests of this acid after dilution showed i t t o be free from sulphuric and selenous acids. X second preparation of the acid n-as made b y fusing the purified selenium dioxide with potassium nitrate and obtaining potassium selenate. To a dilute solution of the fusion lead nitratc was added, insoluble lead selenate being formed. This precipitate n-as thoroughly washed with water after which i t was suspended in water an4 treated ith hydrogen sulphide. The lead sulphide obtained was remo\red bj- filtration, and the resulting dilute solution concentrated under diminished pressure as in the first preparation. The resulting acid proved t o be free, as shown by careful tests, from sulphuric and selenous acids. The puritj- of the acidi u s 5 also ascertained by evaporation on platinum foil and subiequent ignition, no residue m s found in any case, showing sbsence of nonvolatile impurities. The water used in making the dilutions for the weaker acids was distilled three times, once from alkali and once from acid. The acid n a s introduced into a Sprengel pycnometer and the latter placed in a thermostat whose temperature was maintained a t 20' t o within one-tenth of a degree, by a temperature control. It was measured a t this temperature
after n hich the pycnometer containing the acid n a i ireighed at room temperature. The eight, used JT ere carefull\- adjusted in connection with t h i i xroi-k, and the iieigliingi qiven art. corrected to 4' and Yacuum. The specific yrax-itic\ gis-cn arc in t h e liquid iiatc at 20' ref?;-red i o thc dcniity of n a t e r at 4 O .
The strength of the acid \\-ai determined b>-transferrin< i: portion from the pycnometer and reweighing -liter dilution ivith the appropriate amount of water it was titrated with a tenth noriiial solution of iodiurn carbonate, using niethJ-1 orange as the indicator. The iodiuni carbonate solution was prepared from repeatedly crystallized and ignited sodium bicarbonate, and was compared lvith a standard solution of sulphuric acid whose content had been determined gravimetricallJ- I n the determination of the strength of the selenic acid. appropriate weights n-ere taken so that the error of titration should not exceed 0.08 percent of the selenic acid content. XI1 of the determinations have been made in duplicate.
M . E . Diemer and Victor Lenhev
508
Results by determination.
20°
- Vacuum 4 O
Specific gravity
Specific gravity
Percent
I 0048 I 0083 1 1 1 1 1 1 I I
I 1 1
0
1 2
0177 0247 0332 0393 0496 0553 0608 0710 0768 0904 0974 I040
s,
1 I
-
3138 3300
1
3401
' 1
20
I I
4306
66
I2 j0
I
I3 48 14 2 2 15 54 16 67 17 79 18 48 I 9 07
I
4663 486j
8716 1 9053 1 9209 I 9396 I 9610 I 9810 I 9953 2 0235 2 062j 2 0709 2 1160 2 I422 2 I599 2 1831 2 2008 2 2357 2 2552 2 2833 2 3117 2 3340 2 3762
I 5012
5281 5389 5590 5795 5870 6029 6112 6410 6498 6618 6937 7030 7169 7472 764' 7960 8042 8277
1 1 I I I
22
~~
5154
I
I
48
81 54 23 6 3 24 88 25 94 26 7 2 27 31 28 26 29 00 30 I O 31 40 32 82 33 30
4789
I
I
1 I
1 I I I
I I I -~
I
8405
I
3502 3669 1 3752 I 3595 I 4021 1 4155
4284
20 21
I
I
1
II
2461 2546 2684 2813 2971 3028
1 I
I
I O Oj
1 I993 I 2105 I 2210 I 2290 I 2356
I
1
6 62 7 37 8 01 9 33
1 I332 1 '438 I 1503 I 1561 I 1692 I I818 I 1888
I I
jS
3 60 4 50
I I 1110 I 1231
I
89 33
2
4115
2 2
1360 4598 4765 4882 5144 5445 5647 5827 5925
2
2 2 2 2
2 2
68 69 70 71
08 37 80 42
72
64
73 60 7 1 38 7 5 08
76 2 1 77 66
78 I 1 79 95 80 83 81 59 82 j 8 83 I I
84 34 8j I O 86 08 87 35 88 14 89 5 0 90.35 91 50
92 93 94 95 96 97 98 99
83 42
26 28 90 66 60 20
__
Results from selenic acid prepared from lead selenate _ _ _ - ~~- -~ _ 1 0533 j 12 1.5898 70 12 I ' 2.2300 84 I j I 2429 1 28.06 1,
',
~
,
Sfiecific Gravity o j Selenic A c i d
~
Interpolated results
Given at
Specific gravity
Percent
20° --To
509
Vacuum
~-
Specific gravity __
Percent
~
1.000
~
2
12
2
92
I .230
26 30 26 84
3 62 4 16
1 '235 I . 240
27 2s 27 7 0
4 70
I .2 4 j
5 32 6 OS 6 66 7 34 7 92 8 j6 9 20 9 82
I.2jO
28 28 29 29 29 30
09 I j6
I.02j
I.0jO I .Ojj
I ,060 I .06j 1.070
.07j I ,080
10
I ,085
I1 0 2
I ,090
11
1.09j
I2 20
I .I00 I . IOj 1.IIj
88 13 j8 I 4 14 14 66
I .I20
Ij 20
I . 125 I . 130 I ' I35
15 74
I
I .I 1 0
I . 140 I
'
I45
I.Ij0 I.Ijj
I .160 I . 165 I .170 1.17j I . 180 I. 18j I .190 1
'
19.5
I.200 I . 205
-
1.210 1.215 I .2 2 0 1.223
1.005 1.010 I . O Ij 1.020
I ,030 1.035 1.040 I ,045
~~
44 62
12
16 32 16 86 17
38
I 7 90 18 44 18 92
I9 48 20 0 2
20 jS 2 1 08 2 1 60 22 2 2
66 23 18 23 7 0 24 26 22
I.2jj I .260 I .26j
1.270 1.27j 1.280
1.28j I .290 I ,295 I . 300
1.305 I ,310 1.315 I ,320 1.325 1,330 1.335 1 ' 340 1.345 I ,350 1.355 I . 360
I .36j
1.370 1.375 I ,380 I .38j I .390 1 395 1.400 I ,405 1.110
1.415
Specific gravity
24 84 30 25 84 2 j
18 j8 06 44 82 26 30 76 31 26 31 74 32 18 32 64 33 08 33 50 33 92 34 36
34 8 2 33 26 35 72 36 IO 36 43 36 88 37 34 37 80 38 24 38 66
39 1 0 39 50 39 98 40 06 40 66 41 IO
41 56 41 98 42 36 42 7 8
Percent -__
~
1.420
1.425 1.430
1.435 1.440 1.445 I.4jO
1,455 I ,460 I .46j 1.470 1,475 1.480 I .48j I . 490 1.495
43.16 43 56 43 94 44.32 '
'
44.52 4j.oo 45.32 45.68 46.04 46.36 46.70 17.01 47.32 47.66 47 98 '
I ,j I 0 I .j1.j
48.28 48 54 48.92 49.30 49.68
1 ,j 2 0
j0,02
I .j25
50.34
I . j00 I .j o j
I .j30
jo.68
1 ,j,15
j1.04
I .j 4 0 I.jj0
j1.38 j I .66 j1.98
1,555
52.28
545
1
j2.56 ,j2.88 j3.28 53.56 1 575 I . j80 53.94 I . j8j 54.30 I . j90 54.62 1 595 54.92 I ,600 55.28 I .60j 55.62 I .610 55.96 1.61j 56.30 I ,620 j6.60 I ,625 56.88 I . j60 I .j6j I .j 7 0
'
M. E
jI O
Specific gravity
1.630 1,635
,640 I ,645 I
1.650
1.635 I ,660
.66j ,670 1.675
I I
I ,680 I ,685
,690 I .69j
I
I . 700 I . 705 I . 710 I .j I j I .720
I ,725
730 1.735 1
'
I.740
1.745 1.750 I 7.55 I .760
1.76j 1
'
770
1.775 I .780
1.78j 1 790 1 795
Percent
I
bgj I Sho I 86;
--
3
I
70
i 8 04 58 4; j8 SD 59 24 59 j 6 59 74 59 94 60 18
I
Specjfic gravity 2,070 -7
073
2.080 2 . 08j
I
870
I
h7j
2.090 2.095
I T I
880
2 . IO0
88j 890 895
2.105 2.110
2.115 2 . I20 2.125
60 j8
1 I 900 I C)Oj I 910
60 bo 61 06
I 91.5 I ()20
2.135 2.140
61 36 61 64
1
y2
