Colorimetric Determination of Nickel in Bronzes G.HAlM AND B. TARRANT, A r c Manufacturing Co., A method is described for the colorimetric determination of nickel
Ltd., London W.12, England
(16) had attempted to separate copper and nickel by means of iron powder. This was tried out but results were not very promising. S e x t , an attempt & a s made to reduce the copper by means of a sugar solution in the presence of alkaline sodium potassium tartrate. This reaction is commonly used for the determination of sugar in urine and it was considered that it might well be applied in the reverse direction. The teats were fairly successful and the only disadvantage appeared to be caramelization of the sugar which made it necessary to boil the solution afterwards with nitric acid in order to destroy the color. Finally, another method was investigated using a solution of ammonium hypophosphite as reducing agent. This effectively precipitates the Copper at low acid concentrations, yielding a precipitate which is easy to filter. Although the copper is not quantitatively removed in this way, the small amount which remains does not seriously affect the subsequent colorimetric determination of nickel. An excess of hypophosphite has no influence on the reaction, as sufficient iodine is added for its complete oxidation.
i n bronzes. Copper is separated by precipitation with ammonium hypophosphite and subsequent filtration. The nickel is then determined b y measurement of the color produced b y dimethylglyoxime in the presence of citric acid, iodine, and ammonia. The method i s rapid (one determination can b e completed in less than 30 minutes) and of sufficient accuracy for routine purposes.
V
ARIOUS color reactions have been suggested for the colorimetric determination of nickel but, dimethylglyoxime is so far still t,he best, reagent for this particular purpose. This reaction is based on the fact that a red or reddish-brown solution is produced when dimethylglyoxime is added to an alkaline solution containing nickel, provided that it has previously been treated with an oxidizing agent such as bromine water or iodine solution. The colored compound is nickelic (IV) dimethylglyoxime. Its color depends on the method of preparation-i.e., whether the oxidant was added to the solution when it was still acid or after it had been made alkaline. Feigl (3)first described this reaction and Rollet (14) suggested a few modifications in order to make it suitable for colorimetric purposes. Subsequent investigators have used it for the determination of nickel in steel ( 2 , 6-12, 14, 16), where its use has become extensive. The interference of iron can easily be eliminated by adding citric or tartaric acid. Hon-ever, the method is not directly applicable in the presence of considerable amounts of copper, and as far as the present authors can ascertain, there have been only three methods described in the literature for its applicittion to the determination of nickel in bronzes (1, 4,13).
REAGENTS USED
Ammonium hydroxide, specific gravity 0.88. Ammonium hypophosphite solution, 5y0. Citric acid solution, 10%. Dimethylglyoxime solution, lyOin alcohol. Iodine solution, 0.1 'V; 12.69 grams in 50 ml. of water containing 25 grams of potassium iodide. Solution made up to 1000 ml. Nitric acid, 1 to 1. PROCEDURE
Transfer 0.1 gram of fine drillings of the alloy to a 100-ml. beaker and add 2 ml. of nitric acid. Heat until solution is complete and then evaporate gently until a greenish color is obtained. Dilute to 20 ml. with distilled water and add 5 ml. of ammonium hypophosphite solution. Heat to boiling and boil for 3 minutes, then remove from hot, plate and allow to cool. Filter through a Whatman S o . 541 filter paper (11-cm.) and wash with tepid water until bulk is approximately 1-50 ml. Cool the filtrate, transfer to a 250-mi. volumetric flask, and make up to the mark. Transfer 25 ml. of this solution to a 100-ml. volumetric flask and add in the following order, shaking well after each addition:
Haywood and Rood (4)recommend the direct colorimetric determination of nickel in the presence of copper. By the use of special filters and a suitable blank the difficulties arising from t'he presence of copper are overcome, but this method can be used only for nickel contents up to 5%. There is an earlier reference by Dietrich (1)to a similar method, but apart from stating that nickel is determined in an aliquot portion of the solution used for copper, the only information given is that bromine water, ammonia, and dimethylglyoxime are required, Results could be obtained within 10 to 15 minutes for nickel contents up to 15%. Ochotin and Sytschoff (13) developed a method for the colorimetric determination of nickel in alloys, which they claim to be rapid and accurate enough for routine analysis. But they state that if copper is the major constituent of such an alloy a separation-e.g., by electrolysis-has to be carried out although this separat,ion need not be quantitative. After removal of the copper the nickel is precipitated by dimethylglyoxime. The solution containing the precipitate is then transferred t o a separating funnel and treated with ether, with the effect that the entire precipitate becomes dispersed in the ether. The aqueous solution is then drained off and alcohol and collodion are added to the ether suspension. The resulting colored solution is compared with standard solutions of known nickel content prepared under similar conditions. This method was tried out but the separation with ether mas tedious and invest,igations to find a more practical method were continued.
10 ml. of citric acid 2 ml. of iodine solution 10 ml. of ammonium hydroxide solution 4 ml. of dimethylglyoxime solution
Finally make up to 100 ml. with distilled water. Shake the flask well.and allow to stand for a t least 10 but not more than 30 minutes, and measure the color produced by means of a Zeiss Pulfrich photometer, using the photometer filamentolamp with filter S53 (having a mean transmission of 5300 A.), and distilled water as comparison. (Any other type of colorimeter may be used with suitable filters.) The method as described above was found to be applicable for nickel contents up to 5%. For nickel contents between 5 and 10% a 10-ml. aliquot should be taken and the result multiplied by 2.5. For nickel contents above lo%, proportionately smaller aliquots should be taken. This method was first investigated on standard solutions containing a known amount of nickel and copper (Table I). Solution A contained 10 grams of copper per liter and solution B contained 0.2 gram of nickel per liter. These solutions were mixed in the proportions indicated and treated in the way described above. The graph based on these figures was found to be a straight line passing through the origin, proving that the color is strictly proportional to the concentration of nickel, and thus truly follows Beer's law.
Since the method for steel was not directly applicable to bronzes on account of the interference of the copper, the problem was to find a quick method of separating this element. As small quantities of copper are not detrimental, such a separation need not necessarily be quantitative. The usual methods of separating copper-i.e., by electrolysis or by gassing with hydrogen sulfidewere not adopted, as the former requires the use of additional apparatus and the latter is objectionable on account of the obnoxious fumes of the hydrogen sulfide, and the tendency of copper sulfide to become colloidal makes it difficult to filter. A search through the literature was, therefore, carried out to find other suitable methods of separation. I t was found that Turbin 51
52
INDUSTRIAL AND ENGINEERING CHEMISTRY Table
1. 2. 3. 4. 5. 6.
I. Determination of N i c k e l in Standard Solutions K
Solution Ni, Mg. Cell, htm. Reading A 5 ml. B 1.0 30 0.36 A 10 rnl. B 2.0 30 0.76 A 15 ml. B 3.0 10 0.36 A 20 rnl. B 4.0 10 0.49 A 25 rnl. B 5.0 10 0.63 A 30 ml. Ba 6.0 20 0.58 10-ml. aliquot taken and reading multiplied by 2.6; hence: Adjusted coefficient = 0 . 7 2 5
10 ml. 10 ml. 10 ml. 10 ml. 10 rnl. 10 ml.
+++ ++ +
Table Standard
Xi (from Standard Graph)
Cell Reading 30 30 30 10 30 30 10 10 30 30 30 30 30
0.21 0.99 1.00 0.40 0.50 0.02 0.63 0.60 0.84 0.78 1.22 0.50 1.30
Ni (Gravimetric)
K
%
%
0.07 0.33 0.33 0.40 0.167 0.34 0.63 0.60 0.28 0.26 0,407 0.167 0.433
0.55 2.67 6.75 7.98 1.37 2.76 5.13 4.90 2.27 2.10 3.30 1.34 17.6
0.50 2.66 6.72 7 92 1135 2.75 5.10 4.88 2.22 2.05 3.28 1.14 17.5
metric values, the greatest accuracy being found for nickel contents above 3y0. The time required for a single determination is approximately 30 minutes, and very much less if a batch of samples is investigated at the same time. ACKNOWLEDGMENT
The authors wish to express their thanks to the Mond Nickel Go., Ltd., and to Langley Alloys, Ltd., which provided all the samples used in the course of this investigation.
II. Determination of N i c k e l in Standard Bronze
Mm. HAR HAS HAT HAU D T D 174 D T D 164 D T D 197 D T D 412 D T D 498 D T D 504 P-bronze hln-bronze Ni-bronze
0.12 0.253 0.36 0.49 0.63 0.725
Vol. 18, No. 1
LITERATURE CITED Deviation
% +0.05 +0.01 ’ +0.03 +0.06 f0.02 +0.01 +0.03 +0.02 +0.05 S0.05 +0.02 +0.20 f0.10
The method was then tried out for a number of standard bronzes, the nirkel content of which had previously been obtained gravimetrically (Table 11). I n the case of the high-nickel bronze, the solution was made up t o 500 ml. and a 10-ml. aliquot taken. The reading was then multiplied by 5. The results corresponded well with the gravi-
(1) Dietrich, K., Giesserei, 30, 13 (1943). (2) Dietrich, K., and Schmitt. K. Z., 2. anal. Chem., 109, 25 (1937). (3) Feigl, F., Ber., 57, 758 (1924). (4) Haywood, F. W.,and Wood, A. A. R., “Metallurgical Analysis by Means of the Spekker Photoelectric Absorptiometer”, pp. 85-7, London, Adam Hilger, 1944. ( 5 ) Hummon, C. G., Steel, 114, No. 25, 97 (1944). (6) Jones, B., Analyst, 54, 582 (1929). (7) Juza, R., and Langheim, R., Angew. Chem., 50, 255 (1937). (8) Maassen, G., Chemie, 56, 234 (1943). (9) Makepeace, G. R., and Craft, C. H., IND.ENG.CHEM.,ANAL. ED.,16, 375 (1944). (10) Mauzy, H. L., and Yellin, H., Metal Progress, 45, 689 (1944). (11) Mehlig, J. P., IND.ENG.CHEM.,ASAL.ED.,14, 289 (1942). (12) Murray, W. M., and Ashley, S. E. Q.,Ibid.,10, 1-5 (1938). (13) Ochotin, V, P., and Sytschoff, A. P., Z. anal. Chem., 90, 109 (1932). (14) Rollet, A. P., Compt. rend., 183, 212 (1926). Delo, 11, 173 (1935). (15) Turbin, L., I~~aslobolno-Zhirozoe (16) Vaughan, E. J., “Further Advances in the Use of the Spekker Photoelectric Absorptiometer in Metallurgical Analysis”, pp. 3-6, London, Institute of Chemistry, 1942.
Removal of Peroxides from Organic Solvents WALDEMAR DASLER AND CLIFFORD D. BAYER Nutrition Research Laboratories, Chicago, 111. A rapid and efficient method for removal of peroxides from organic solvents b y means of activated alumina is presented. Since n o moisture i s added, the method i s directly applicable to dioxane and anhydrous solvents.
THE
autoxidation of ethers and certain other organic solvents during storage gives rise t o the formation of peroxides. The distillation of any of a wide variety of ethers containing appreciable quantities of peroxide may result in dangerous explosions (14). Peroxide-containing isopropyl ether appears t o be particularly hazardous in this respect, violent explosions of its distillation residues having occurred as a result of heating at temperatures well below 100” C. or even from mechanical shock alone (3,7 ) . The octane numbers of synthetic gasolines are appreciably lowered by the formation of peroxides during storage, but can be largely restored by removal of the peroxides (1, I f ) . The use of peroxide-containing liquids as solvents for substances which are easily oxidized necessitates the prior removal of the accumulated peroxides. A large number of methods for accomplishing such purifications have been proposed from time t o time. Peroxides, aldehydes, unsaturated compounds, and acids can be effectively removed from impure ether by shaking with aqueous silver hydroxide precipitated in szfu with a n excess of alkali (12). A commonly used laboratory method of freeing ethyl ether of peroxides consists in treating the ether with a n aqueous solution of
ferrous sulfate (14). Aqueous solutions of sodium bisulfite, acidified potassium iodide, sodium sulfite (I.$), and potassium permanganate (?‘) have also been recommended. Peroxides may also be eliminated from ether by distilling over either alkaline pyrogallol’or alkaline permanganate and then passing a fine spray of the condensed ether through a strongly alkaline solution of either reagent (8). All these methods have the disadvantage of necessitating the addition of water which, if an anhydrous solvent is desired, must subsequently be removed. Furthermore, they are not suitable for the treatment of many water-miscible liquids such as dioxane or some of the monoalkyl ethylene glycol ethers (Cellosolves). The purification of ether with alkali metals (10) or hydroxides (6, 10) eliminates both peroxides and aldehydes but, in common with the above methods, also requires a distillation procedure. Two recently developed methods for destroying peroxides are applicable t o dioxane as well as t o some of the acyclic ethers (3). These consist in shaking the dioxane with stannous chloride and distilling off the dioxane and refluxing with lead dioxide and filtering through a tight filter paper. The only previous report on the use of an adsorbent for the elimination of peroxides in ether appears to be that of Rae (9) who found that when peroxide-containing ether was shaken with 1.1yo of animal charcoal and allowed to stand, the peroxides gtadually decreased and in 54 days finally disappeared. Harris and Welch ( 4 ) found that certain carbons removed the compounds which were responsible for a positive Kreis test in a cottonseed oil. Activated alumina has previously been recommended for the continuous commercial drying of organic liquids ( 2 ) . I n connection with the chemical study of certain oxygen-labile steroids in these laboratories, it Tvas found that peroxides could be completely and quickly removed from many organic solvents by merely passing them through a vertical column of activated
