INDUSTRIAL A N D ENGINEERING CHEMISTRY
January, 1925
though no figures are giver1 for larger quantities of aniline, the method is accurate for a 2.0 per cent solution and using 1 N sulfuric acid.
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Sample 1 2 3 4 5 6 7 8
Sample 1 2 3 4 5 6
7 8
TABLEI-BROMOPHENOLBLUEA N D THYMOL BLUE -BROMOPHENOL BLUEF-- T H Y M OBLUE L 0.1 N Aniline Aniline Aniline 0.1 N found Per cent found Per cent NaOH present HiSOa Gram Cc. Gram error Cc. Gram error 0,2052 22.05 0,2051 0.0 23.25 0,2162 5.3 0,1846 1 9 . 8 5 0,1846 0.0 22.4 0,2083 1 2 . 7 0.1642 17.70 0.1646 0.2 1 8 . 1 5 0.1689 2.8 0.1436 1 5 . 3 5 0,1428 0.3 15.5 0,1442 0.4 0,1231 1 3 . 2 5 0,1232 0.0 14.95 0,1390 1 3 . 0 0,1026 11.15 0,1037 1.0 12.5 0.1162 1 3 . 2 0.0821 8.75 0.0814 0.8 9.85 0.0916 1 1 . 5 0,0410 4.6 0,0428 4.4 7.25 0.0670 .. .
TABLE 11-POTASSIUM BROMATE-BROMIDE Per cent Aniline found Aniline present 0.1 N &SO4 Gram cc. Gram error 0.14 22.1 0.2055 0.2052 0.7 19.7 0.1832 0.1846 17.45 0.1621 1.3 0.1642 0.55 15.35 0.1428 0.1436 13.45 0.1261 1.6 0.1231 10.85 0,1009 t.6 0.1026 J.0 9.25 0.0860 0,0821 17.0 5.15 0.0479 0.0410 ~~
Somewhat more uniform results, although having a larger divergence from the known amounts, were obtained with p-dimethylamidoazobenzene. Eight drops of a 1 per cent alcoholic solution are used. The color change is from yellow to rose red, and approximate results may be obtained, as with bromophenol blue, without the use of a standard aniline solution. Such a standard is, however, advisable for accurate determinations. I n using this indicator the end point is marked by the entire absence of any yellow color. The rose red color when obtained may fade out; hence additional 0.1 N sulfuric acid should be added, 1 or 2 drops a t a time until the red color becomes permanent. Table I11 shows the results obtained with this indicator, a standard aniline solution being used for color comparison. Sample 1 2 3 4 5
6 7 8
TABLEIII-i?-DlMETHYL.4MIDOAZOBENZENE Aniline found Aniline present 0.1 N HzSOa Gram cc Gram 0,2055 22.1 0.2052 19.9 0,1846 0.1852 0.1637 17.6 0.1642 0,1432 15.4 0.1436 0,1223 13,l5 0.1231 0,1037 11,l5 0.1026 0,0842 0.0821 9.05 0,0410 0.0451 4.85
.
Per cent error 0.1 0.3 0.3 0.3 0.6 1.0 2.0 10.0
The definite increase in percentage error may mean that this is a more satisfactory indicator than broinophenol blue, in that an error curve may be plotted for reference. The results with Congo red (Table IV) were found to be more accurate than with thymol blue, but less so than with the other two indicators. The details of the Julius procedure are unknown to the writer, but good results were obtained by use of the following precautions: A standard aniline solution is absolutely necessary and the same amount of indicator must be used in both standard and unknown. It is well to use beakers of the same size and free from irregularities. The use of'Nessler tubes increases the accuracy somewhat. The titrations were made in the same may as the previous determinations, 5 drops of 1per cent Congo red solution in water being used. It should be noted that the end point of Congo red with aniline is marked by the complete removal of any reddish tinge and the appearance of a definite purple color in the solution. IV-CONGO RED TABLE Sample 1 2
3 4 5 6
7 8
Aniline present Gram 0,2052 0.1846 0.1642 0,1436 0.1231 0,1026 0.0821 0.0410
0.1 N &SO4 cc. 21.9 19.9 17.8 15.5 13.0 10.9 8.4 4.3
Aniline found Gram 0.2037 0.1851 0.1655 0,1442 0,1209 0,1014 0,0781 0,0400
Per cent error 0.7 0.2 0.8 0.4 1.7 1.1 4.8 2.4
63
Results with Toluidines Since such favorable results were obtained with aniline, it was thought that equally good results might be secured with the toluidines.
Sample 1 2 3 4
Sample 1 2 3 4
TABLE V-BROMOPHENOL BLUE o-Toluidine o-Toluidine present 0.1 ' h &SO4 found Gram cc. Gram 0.0500 4.50 0.0481 0.1000 9.35 0.1000 0.1500 13.95 0,1492 0.2000 18.7 0.2000
Per cent error 3.8 0.0 0.5 0.0
TABLEVI-~~-DIMETEYLAMIDOAZOBENZENE Toluidine Toluidine present 0.1 N HnSO4 found Per cent Gram cc. Gram error 9.35 0.1000 0.0 0.1000 14.25 0.1525 1.6 0.1500 18.6 0,1990 0.5 0,2000 0.2500 23.0 0.2461 1.6
The results with p-toluidine were less favorable owing to its slight solubility in water, which made it necessary to use large volumes of the aqueous solution, and thus increased the possibility of error. Acknowledgment Thanks are due L. B. Sebrell for assistance in the preparation of this paper, and to C. W. Foulk, of Ohio State University, for his criticism of the manuscript.
Water Circulation Device'
'
By Robert E. Jefferson 70 LINWOODR O A D HANDSWORTH, , BIRMINGHAM, ENGLAND
r
T sometimes happens that a circulation of water is desired through a vessel not provided with an outlet, and
perhaps from some cause it is impossible to make a suitable aperture to run off the water. The apparatus shown in Fig. 1 was designed by the writer in such a case.
L
3
A FIG.1
lF
A is the vessel through which the water had to circulate. B is the inflow tube coming from an elevated constant head apparatus, C. Water also flows from C through tube D to the automatic siphon E and fall tube, F . G is a hole-not too small-in the siphon E and situated a t the desired water line. H is the waste water from the constant head C. J is the supply. It is important that tube B is slightly higher than D. This apparatus was slightly modified to wash the mercury surface in the mercury bath of a Bone and Wheeler gas analysis apparatus. 1
Received September 26, 1924.
