THE USE OF A ZINC WIRE SPIRAL AS A JONES REDUCTOR G. FREDERICK Snrrrn AND JOSEPH &CB, UNIVERSITY OF ILLINOIS, URBANA, ILLINOIS
Introduction The amalgamated granulated zinc Jones reductor is used extensively in the volumetric determination of the following elements after reduction to the lower valences indicated, iron ( l l ) , titanium ( I l l ) , molybdenum ( I l l ) , vanadium ( l l ) , chromium ( l l ) , and uranium (< IV). Because of the previous inability to obtain pure zinc wire, granulated zinc has been replaced with coils of aluminum wire or aluminum sheet for some of these reductions, particularly that of iron, because of the obvious disadvantages in the use of granulated zinc. The aluminum so used invariably contained enough iron to make a troublesome blank correction necessary. This present paper has for its object the description of the use of pure zinc wire as a Jones reductor, calling attention to its ready availability and indicating necessary precautions in its preparation for use and testing its accuracy in actual service as a substitute for granulated zinc in the usual type of Jones reductor. Zinc Wire Spiral Analyses, Preparation of Spiral and Amalgamation For a description of the use of the old type of Jones reductor and hibliographic references to the same, the paper by Lundell and Knowles (1) serves. Further references to the literature are unnecessary. As far as could be learned no previous description of the use of zinc wire to substitute for the granular zinc of the Jones reductor has been given. Zinc rod is unsuitable both because of insufficient surface exposed and an unsatisfactory porosity especially after a short period of use. The zinc wire used in the present paper was supplied through the courtesy of W. H. Bassett, metallurgical manager of The American Brass Company, Waterbury, Connecticut. A second sample was obtained through the assistance of W. T. Isbell of the St. Joseph Lead Company, Bonne Terre, Missouri. The analyses are found in Table I. TABLE I
T h e Analysis of Commercial High-Grade Zinc to Be Used in Spiral Zinc Wire Reduction Motwid
Bunker Hill Zinc St. Joseph Lead Co. Anaconda Zinc American Brass Co.
% Pb 0.0075
% Cu 0.0006
% Fs
AGb,Sn
0.0017
Free
% Cd 0.0019
% AI
0.0007
0.003
Both samples of zinc shown in Table I proved satisfactory for the preparation of zinc wire spiral reductors. The samples were supplied in the form of wire approximately 3 mm. in diameter, 10 cm. of which weighed approximately 5.7 grams. A coil made from 715 mm. weighing 48.5 grams was made by turning lo1/%turns around a 19-mm. cork borer with 2948
VOL.7. No. 12
WIRE SPIRAL AS JONES REDUCTOR
2949
a vertical extension of 4-5 inches to serve as a handle to insert and withdraw the reductor in use. A coil so formed just passes conveniently through the neck of a 300-cc. Erlenmeyer flask. Zinc wire of the purity employed shows a marked Vendency to crystallize due to bending. If annealed at 125°C. for a few hours this property is lost to an appreciable extent but upon solution in acid, small portions scale off into the solution being reduced and defeat the attempt to remove and wash the entire excess of zinc employed. Annealing together with amalgamation prevents both these tendencies completely. The zinc spiral reductor is amalgamated by immersion during a tenminute interval in a 10% solution of mercuric nitrate acidified with 5% by volume concentrated nitric acid, using the solution at room temperature and shaking the 300-cc. Erlenmeyer flask containing the spiral and solution at frequent intervals. The solution for amalgamation should just immerse the spiral part of the coil in the amalgamating liquid. The gain in weight of the coil, when corrected for the amount of zinc dissolved, shows a spiral reductor treated in this way to be amalgamated to the extent of 1-2%. A coil so treated while fairly flexible breaks if distorted too highly following amalgamation. Such coils are known to be more active if treated by immersion in an acid solution containing a few mg. of platinum. The coils used in this work were not so treated. The per cent amalgamation increases in a given coil during use because of the solution of zinc but as with amalgamated granular zinc an increase to 5% amalgamation does not interfere with the use of the spiral reductor. The Procedure in the Use of the Spiral Zinc Wire Jones Reductor The spiral zinc wire Jones reductor is employed as follows: the sulfate solution of ferric iron in 5 1 0 % sulfuric acid solution and of normality from 0.01 to 0.03 in iron and of approximately 200 cc. volume is placed in a 300-cc. Erlenmeyer flask, the zinc spiral introduced and the flask covered by an inverted crucible cover, and brought just to the boiling point and allowed to digest at just the point of faint ebullition. As soon as the ferric ion color of the solution has disappeared, the heat is maintained during an interval of 15 minutes and the sample rapidly cooled to room temperature with the zinc spiral still in the solution. The spiral is then removed from the flask, washed with a generous stream from the wash bottle, allowing the washings from the coil to return to the flask. The solution is then treated with a few cc. of sirupy phosphoric acid and titrated with standard potassium permanganate. Factors Associated with the Use of the Zinc Wire Spiral Reductor
A comparison of the advantages and disadvantages in the use of the spiral zinc wire reductor as substituted for the granular zinc reductor is of
2950
JOURNAL OF CHEMICAL EDUCATION
DECEMBER, 1930
interest. The simplicity of apparatus and materials hoth in preparation and in actual manipulation makes the use of the spiral reductor advantageous. These advantages are apparent from the above discussion by reference to the photo-reproduction of hoth reductor assemblies given in Figure 1. The main difference between the two methods consists in the fact that reactions of the old type of granular zinc can he carried out in the cold (I) and that there is a saving of time using the old process. This saving of time is unimportant as compared to the increased amount of attention required for the old method. By the use of the zinc spiral reductor any number of reductions can he carried out a t the same time with no increase in required attention. This is by no means the case using the old process. The separation of the solution for titration is much more conveniently carZinc Spiral Jones ried out using the spiral reReductor Reductor ductor which offsets its disCOMPARISON OR APPA~ATUS advantage of being slower in reaction than the amalgamated granular zinc, which has amuch higher surface of reaction per unit weight. The variables in the use of the spiral zinc wire reductor covered in the present discussion are: the time, temperature, acidity, and their relation to the efficiency obtained in the ratio of zinc dissolved as compared to the amount of iron reduced. The factors, temperature and acidity, wereeasily disposed of by selecting the boiling temperature and using the same acidity (%lo% by vol. conc. HzS04)as that ordinarily employed with granular zinc reductors.
VOL. 7, No. 12
2951
WIRE SPIRAL AS JONES REDUCTOR
The time and efficiency factors together with the accuracy attained are given in Table 11. Solutions of ferric sulfate were analyzed using the old type of reductor following the directions of Lundell and Knowles (1)with KMn04 as the standard solution. The latter was standardized using pure sodium oxalate in the usual manner. TABLE II The Use of the Spiral Zinc Wire Jones Reductor in the Determination of Iron FeZ(S03.solution = 0.1227 N and 25.00 cc. of this solution diluted to 200 ce. for each experiment. Acidily.
%
IIzSO,
4 5 6 7 8 9 10
WI. Fa Taka",
s. 0.1713 0.1713 0.1713 0.1713 0.1713 0.1713 0.1713
Zn LOSS, 8.
ERi-
Wl. PE
rirnn.
Pound,
Ewo*.
Anrolgonol i o n of
31 60 72 69 51 54 52
0.1689 0.1703 0.1713 0.1715 0.1713 0.1713 0.1711
-0.0024 -0.0010 5 0 . OW0 -0.0002 *O.OOOO 1 0 .OOOO -0.0003
1 2 1 2 1 1 1
70
0.319 0.150 0.139 0.148 0.198 0.186 0.191
2%.%
8. P S
&
From an examination of Table I1 it is observed that for best results an amalgamation of approximately 1% and an acid composition of 6-10% by volume concentrated HISOa are used. The highest efficiency is obtained using a &7% acidity. Low results are obtained for a 30-minute reduction period if the acid concentration is 5% or less. Further tests with the study of the time variable are found in Table 111. TABLE Ill The InRuence of Time of Reaction on the Efficiency of the Spiral Zinc Wire Reductor 25.00 cc. solution No. 1 Fe.(SO,)a = 27.14 cc. 0.1233 N KMnO, = 0.1339 N. 25.00 cc. solution No. 2 Fel(SO& = 45.75 cc. 0.1233 N KMn04 = 0.2276 N. Acid concentration 5% by volume conc. HzS04. Amalgamation of zinc wire 1.75%. Dilution of FeJSO& -. ... to 200 cc. 25.00 rc. 901. Pe,(SO&
Solution 1 Solution 2
Time far rcdurlion P n i o d of lo rolor- dipaqion, Ern, mi". m'n.
15 15 17 15
20 23 25 30
KMnO. Re-
puirad, CC.
27.12 45.44 45.60 45.72
Error,
Zinc reducror 85-
K&O
