1052
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Vol. 13, ‘Ma11
Solid Sodium Hydroxide as an Absorbent for Carbon Dioxide in Steel Analysis’ By G . L. Kelley and E. W.Evers CHEMICAL LABORATORY, MIDVALES T E E L &
CO., hTICETOWN
ORfiNANCE
.A solution of potassium hydroxide has long been used as an absorbent for carbon dioxide in the determination of carbon by combustion. Bulbs filled with such a solution were capable of absorbing completely about 1 g. of carbon dioxide. This absorbent has been partly superseded in recent years by soda lime, which in the various bulbs used for the purpose would absorb from 1 to 4 g. of carbon dioxide, depending upon the capacity of the bulb. In an earlier article,2 one of us described an absorption tube devised by H. L. Frevert, and a new absorbent for carbon dioxide called by the writer “soda-asbestos.” This material was capable of absorbing about 20 per cent of its weight of carbon dioxide, which in the different types of bulbs used as containers amounted to from 6 to 15 g. of carbon dioxide. The reagent would be prepared from cheap grades of asbestos having a market price of about $150.00 per ton, and technical grades of sodium hydroxide, by heating a moistened mixture of these materials. Since the appearance of this article, Stetser and No1 ton3 have described apparatus for the determination of carbon in steel, and give their experience with a modified variety of “sodaasbestos” which they have devised. The absorption tube which they have proposed differs from the Frevert tube only in its proportions. Stetser and Norton recommend the use of their product without any additional material to absorb water. The writers have not considered this a safe procedure to employ with “soda-asbestos.” When the mixture of sodium hydroxide and asbestos is practically free from water, its effectiveness as an absorbent is much less than when a small amount of water is present. The freshly prepared mixture gives up its water very slowly, but as the saturation of the bulb is approached, the water is released in increasing amount. . Accordingly, in working with “soda-asbestos” we have placed a layer of calcium chloride a t the exit end of the tube. Owing, however, to the variable and uncertain character of calcium chloride as a dehydrating agent, even this device has not been found capable of yielding uniformly accural e results. Utubes of phosphorus pentoxide placed before and after the absorbing tube show a small loss of water by the latter, amounting to about 1 mg. in the course of a determination of carbon. For the purpose of securing greater uniformity in results, the authors now use phosphorus pentoxide as a drying agent. The Frevert bulb as originally made up did not provide for the use of phosphorus pentoxide, but it has been possible to use this material as a drying agent by attaching a short tube to the outlet of Frevert’s bulb. The tube is provided with a small one-holed rubber stopper a t each end, which permits recharging with Pz06without disturbing the carbon dioxide absorbent A U-tube containing PZOSis placed before the absorbing tube, and the outlet of the latter is connected with a bubble counter containing barium hydroxide. This device serves to indicate the rate of gas flow as well as the saturation of the sodium hydroxide. The accompanying figure shows the Frevert bulb with the phosphorus .pentoxide tube attached. While endeavoring to improve “soda-asbestos” as an absorbent for carbon dioxide the authors decided to test the properties of sodium hydroxide for this application.
It was supposed that lack of surface would seriously interfere, but it was found that it would absorb nearly one-third of its weight of COZ. Coarsely broken sticks of sodium hydroxide do not absorb as much as the powdered form, but thelatter is objectionable because it cakes. The most satisfactory results were obtained with a material which would pass 5-mesh screen, but remain on a 20-mesh screen. Grinding and sifting the sodium hydroxide, especially in moist weather, is very unsatisfactory. Tt is possible to buy small cans of “household lye” in which the sodium hydroxide is somewhat smaller than rice, and which has been found to serve our purposes admirably. This has proved to be far superior to either soda-lime or ‘isoda-asbestos,”
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1 Received
April 8 , 1921. TEISJOURNAL, E (lele), 1038. : IYOW Age, loa (1918),443.
P L A N T , PHILADELPHIA, P A .
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26 7034 CFHM5
It has been poipted out to the authors that W. R. FlemingL has stated that solid sodium hydroxide may be used as an absorbent for COz in the bulb covered by this patent. We believe, however, that this is the first report on its actual application in the absorption of carbon dioxide in connection with. the determination of carbon in steel by combustion. Our experience with this reagent as used for this purpose is based upon its use in a large technical laboratory where several thousand determinations were made in each month over a period of more than a year. Potassium hydroxide would, of course, serve equally well, and it would have the advantage that water is retained better by potassium hydroxide than by the corresponding sodium compound, but it is more expensive and the difficulty of protecting it from moisture during preparation is even greater. A further disadvantage lies in the higher atomic weight of potassium.
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U. S. Patent 1,324,763.
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERINO CHEMISTRY
Nov., 1921
1053
The Determination of Chromium in Ferrochromium by Electrometric Titration' By G. L. Kelley and J. A. Wiley CHEMICALLABORATORY, MIDVALL?STEEL& ORDNANCGCo., NICETOWN PLANT, PHILADELPHIA,PA.
A paper on the determination of vanadium and chromium in steel was published by Kelley and Conant,2 and more recently a paper by Kelley and other collaborators3 describes the determination of vanadium and chromium in ferrovanadium. I n these cases the end-point was determined electrometrically. The present paper describes a method for the determination of chromium in ferrochromium in which the end-point in the titration is taken as the point of greatest change in the oxidation-reduction potential during the titration of the chromic acid with ferrous sulfate. The description of apparatus suited to this determination has been given by Kelley, Adams and Wiley.4 STANDARD SOLUTIONS POTASSIUM DICHROMATE SOLUTION-5.6586 g. Of the recrystallized and fused salt in enough water to make one liter. FERROUS AMMONIUM SULFATE SOLUTION^^ g. of ferrous ammonium sulfate and 100 cc. of sulfuric acid fsp. gr. 1.58) in enough water to make one liter. This should be standardized daily by comparison with the dichromate solution which is used as the standard of reference. HYDROCHLORIC ACID soLuTroN-One part of concentrated acid and three parts of water. SILVER NITRATE SOLUTION-2.5 g. of silver nitrate in enough water to make one liter. A M M O NIUM PERSULBATE SOLUTIO N-1 00 g. arnmonium persulfate and water enough to make one liter.
METHOD Use a nickel crucible of about 60-cc. capacity, preferably fret. from mangancse. Fuse 20 g. of sodium carbonate in the crucible, and during cooling rotate it in such fz manner as to produce a lining on the crucible. When cool, place 16 g. of sodium peroxide in the crucible. Make a hole in the center of this and place in it 1 g. of ferrochromium, ground to pass a 100-mesh sieve. Mix the ferro-alloy with the peroxide by stirring with a stiff platinum wire, taking care that the alloy does not sink to the bottom. Fuse over a blast lamp until fusion is complete, and apply heat enough to maintain the melt in a state of quiet fusion for 3min., rotating gently meanwhile. Avoid fusing the lining as this is detrimental to the crucible. During cooling, cause the molten mass to flow in thin layers on the surface of the crucible. When cold, wipe the outside of the crucible clean. and place it in 300 cc. of water contained in a 600-cc. beaker. Warm to complete the solution of the mass, and remove the crucible after rinsing. Boil the solution a t least 30 min. Cool to room temperature, and add gradually 80 cc. of sulfuric acid (sp. gr. 1.58). Boil 5 min., cool, filter through asbestos, and make the volume up to exactly 1 liter. Analyze the solution as soon as i t is prepared. Remove a 100-cc. portion, add 25 cc. of sulfuric acid, and titrate electrometrically with ferrous ammonium sulfate and potassium dichromate. A modification of the method involves the following procedure: To 100 cc. of the solution, add 25 cc. of sulfuric acid, 10 cc. of silver nitrate solution, and 40 cc. of ammonium persulfate solution. Boil 10 min. after the permanganic acid color appears. Then add 5 cc. of 1 - 3 hydrochloric acid, boil an additional 5 min., cool, and titrate electrometrically with ferrous sulfate. I
Received April 28, 1921.
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I b i d . , 9 (1917),780.
* THISJOURNAL,8 (IQlS), 719. * I b i d , 18 (1921). 939
For the highest accuracy, the potassium dichromate should be recrystallized and fused. The dichromate solution is of such strength that each cubic centimeter corresponds to 2.00 per cent of chromium in a 0.10-g. sample. To calculate, multiply by 2 the cubic centimeters of dichromate solution to which the ferrous sulfate solution used is equivalent. This gives the result directly in per cent. Vanadium is rarely present in ferrochromium in quantities warranting its determination. When it is desirable to determine it, this may be done, after reduction of the chromate and vanadate with ferrous sulfate, by oxidizing the vanadium alone by means of nitric acid. It is then titrated electrometrically with ferrous sulfate. This procedure has already been described elsewhere' by one of us.
EXPERIME NTAI. This method has bee: tested experimentally against pure potassium dichromate and mixtures of dichromate and finely powdered pig iron in which an exactly similar procedure as to fusion and solution was followed. The results are given in the table. I n each case 1.9802 g. of potassium dichromate were used and one-tenth of this amount was titrated. The pig iron contained 0 04 per cent of chromium, for which correction was made. ANALYSISO F DICHROMATE &ONE WITH Chromium Amount Pig Iron Fused with Present SAMPLE Gram NazOz and NazCOs Gram 1 None Notfused 0.7000 2 None Fused 0,7000 3 0.25 Fused 0.7000
PIC IRON Chromium --FoundGram Gram 0.7002 0,7005 0.7002 . 0.7003 0.7008
.. .
This method was checked by oxidizing with ammonium persulfate. A portion of the third solution was treated with 25 cc. of sulfuric acid of sp. gr. 1.58, and diluted to 300 cc. After heating to boiling, 10 cc. of silver nitrate solution and 20 cc. of ammonium persulfate solution were added. After boiling 10 to 15 rnin., 5 cc. of dilute hydrochloric acid were added and the boiling was continued 5 min. Boiling with silver nitrate and ammonium persulfate served to oxidize all of the chromium and manganese, and boiling with hydrochloric acid decomposed the permanganic acid. After cooling and titrating, 0.7001 g. of chromium was found. The procedure was next applied directly to a sample of ferrochromium. After preparing the solution for titration after the fusion witch sodium peroxide, 100-cc. portions were reduced with an excess of ferrous sulfate and titrated with 0.1 N permanganate, correcting the titration with a carefully determined blank. The percentages of chromium found in this way were 63.43 and 63.65. Other portions of the solution titrated electrometrically with ferrous sulfate gave 63.48 and 63.48 per cent. One portion was boiled for 5 min. with 5 cc. of 1:3 hydrochloric acid, and on electrometric titration with ferrous sulfate after cooling gave 63.43 per cent. A portion was treated with an additional quantity of sulfuric acid and oxidized with silver nitrate and ammonium persulfate. The permanganic acid was destroyed with hydrochloric acid, and the solution was cooled and titrated electrometricnlly with ferrous sulfate. The value found was 63.46 per cent. In all of this work where dependence was placed on the oxidation of the chromium by sodium peroxide, a portion of the solution was analyzed as soon as it had been made up to volume. This was found necessary owing to the 1
THIS JOURNAL,11 (1919) 632.
