INDUSTRIAL AND ENGINEERING CHEMISTRY
3 30
TABLE IV. EFFECT OF REDUCINQ AMOUNTOF SELENIUM No. HgSeOs
cc.
HC1
NHiCNS
cc.
(12 N )
H20
CC.
Cc. 2.35 2.70 3.05 3.40 3.75 3.95 4 05 4.07 4 09 4.11 4.13 4.14 4.14 4.14
Total NorVolume mality Solution
cc.
10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0
+ 0.5
:8:8 t 8:; 10.0 f 0 . 5
Good Good Good Good Good Good Faint
7 7 7 7 7 7 7 7 7 7 7 7 7 7
++ i+ +t
VOL. 9, NO. 7
The reaction takes place only slowly at room temperature, much more rapidly a t elevated temperatures, and for small quantities of selenium is complete within 20 to 30 seconds at the boiling point. Acknowledgment
The problem of selenium determinations was f i s t suggested to the author by G. Frederick Smith, Department of Chemistry, University of Illinois. The author wishes to express his appreciation to J. T. Dobbins, Department of Chemistry, University of North Carolina, for his interest in the writing of this paper. Literature Cited
Temperature-Time Variation
I n order to find the lowest temperature at which the reaction begins, a series of experiments was conducted by mixing the proportions of solutions indicated, placing them in a Thiele melting-point tube, heating slowly to the temperature indicated & 1" C., and holding at this temperature for the time indicated. The solution was then cooled to room temperature and filtered, and a portion of the filtrate was heated to boiling prior to testing for complete precipitation. TABLE V. TEMPERATURE-TIME VARIATION Nor- TemHC1 Total mal- peraNo. HzSeOa NHdCNS (12 N ) HzO Volume ity ture Time Filtrate cc. cc. cc. cc. cc. C. Min. 7 40 30 Noreaction 1 0 . 0 29.35 8 . 5 5 0 . 0 1 2.6 7 55 15 1 0 . 0 29.35 8 . 5 50.0 2 2.5 50.0 7 55 30 No.3 1 0 . 0 29.35 8 . 5 50.0 4 2.5 7 60 30 6 2.5 10.0 29.35 8 . 5 50.0 8 5 50.0 7 65 15 +Faint 10.0 29.35 6 2.5 7 70 15 '7 2.5 1 0 . 0 29.35 8 . 5 5 0 . 0
+$
-
From Table V it is seen that the reaction is complete a t this concentration within 30 minutes at a temperature of 60" C.; that with an increase in temperature the time required for completion becomes less; and that the reaction is complete within 15 minutes at 70" C. The reaction begins rapidly at 60" C. A similar experiment showed that the reaction takes place a t room temperature, but is not complete within 30 hours.
(1) Andrews, J . Am. Chem. Boc., 25, 756 (1903). (2) Coleman and McCrosky, IND.ENG.CHIM.,Anal. Ed., 8, 196 (1936). (3) Dudley and Byers, Ibid., 7, 3 (1935). (4) Knight, H.G . , Sigma Xi Quarterly, 25, No.1, 1 (1937). (6) Marvin and Schumb, IND.ENG.CEEM.,Anal. Ed., 8, 109 (1936). (6) Williams and Lakin, Ibid., 7, 409 (1935). R ~ ~ C E I VApril I O D 22, 1937.
Feeding Device for Boiler Compound J. L. SMITH Naval Boiler Laboratory, U. S.Navy Yard, Philadelphia, Pa.
T
HE feeding device illustrated is in use a t this plant for adding boiler compound a t steady rates to boiler feed water. It maintains a constant head and constant rate by floating the intake end of the delivery tube. It is simple in construction and the necessary materials should be found in any laboratory. GLASS TUBE WITH 3 m m BORE S T O P C O C K 7 I - G A LCUT TINOFF CAN
6 mm. I. D 7
/ ,.-Liauio
CONS HEA
-
Interferences
I n order to determine the interfering ions, experiments similar to those previously conducted were carried out in the presence of approximately 100 mg. of each ion shown in Table VI, in the cases of the noninterfering ions the precipitates were filtered off, dissolved in nitric acid, and tested for the metal. I n no case was a positive test for the metal obtained.
LEVEL
1200-GRAM LEADWPSHEW
5- GAL TIN C A N 2
-
RUBBER HOSE
3 mm
I. 0.
TABLE VI. INTERFERENCES Interfering Ion8 Noninterfering Ions
Fe++ Sb+++ S n + + Fe++$ M n + ; C r + + + 41+*+ Zn+*, N i t + , Cot+, Pb+%,Cut:, B i + + t , ' C d + + k, g t + w
Summary
A new reaction has been used in the development of a test €or the selenite ion, and is sensitive to 1part of selenium in 20,,040,000 parts of solution. The sensitivity is much greater (1 part of selenium in 38,168,000 parts of solution) if the solution is allowed to stand for a t least 48 hours. The reduction of the selenite ion is complete in solutions 6 N with respect to hydrochloric acid. There is an exact stoichiometric relationship between the reacting ions.
A 20-liter (5-gallon) and a &liter (1-gallon) tin can, a small glass funnel, copper tubing, a glass stopcock, rubber stoppers, scrap lead, small-bore rubber tubing, and a piece of glass tubing are all the materials needed. The device as illustrated will deliver from 20 to 180 ml. per minute constant rate. Higher or lower rates may be obtained by varying the ballast in the float to vary the head, or by using tubing and stopcock of larger or smaller bore. RECEIVED May 14, 1937
