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INDUSTRIAL AND ENGINEERING CHEMIXTRY
That the poor results obtained with the dehydrated oysters were not to be ascribed to the action of any toxic substance present was evident from the general behavior of the animals and the character of their growth curves. Both were strictly typical of the characteristic results of vitamin deficiency. Furthermore, when yeast was added to the same oyster diet, growth at a satisfactory rate followed, and no symptoms indicating toxicity were noticed. As already mentioned, the oysters used in the experiments described were obtained during the winter. Later, some feeding tests with oysters procured a t other seasons of the year gave results that showed considerable deviation from those herein recorded, particularly with respect to vitamin B. Whether this was due to a seasonal variation connected with differences in the food supply of the oysters or to some other factor, we cannot a t present decide. The fact that the food supply of oysters greatly varies a t different times of the year lends support to the former view. In the tests in which rachitic rats fed the low phosphorushigh calcium diet were given daily 5 grams of frozen oysters, equivalent to 0.8 gram of dry material, approximately half calcification was induced in 15 days, and complete calcification in 20 days. Since oysters contain a significant amount of phosphorus, it might be contended that the calcifying property of oysters as found in these tests could be attributed, not to the presence of vitamin D, but to the superimposed phosphorus contained in the oysters fed. That this was not the case is shown in the following considerations. Oysters also contain considerable calcium, which would proportionally counterbalance any curative effect the phosphorus in the oysters might have. The general effect would be to continue to maintain a low phosphorus-high calcium ratio. In the vitamin A experiments with dehydrated oysters it
Vol. 20, No. 2
was found that this product had little or no effect in curing rats of xerophthalmia, but it did stimulate a decided response in the rate of growth. This can be explained on the ground that during the dehydration the antiophthalmic factor had been destroyed and that the growth response was due to the more resistant antirachitic factor, that had escaped inactivation. Furthermore, it was found that when the ash obtained by incinerating oysters was fed to rachitic rats for 15 and 20 days in conjunction with the basal diet, in a quantity equivalent to the 5-gram daily intake of frozen oysters, the degree of induced calcification was insignificant as compared with that following the daily administration of 5 grams of fresh oysters. I n experiments in which six rats were fed 5 mg. of cod-liver oil daily, half of them receiving in addition the ash equivalent of 5 grams of fresh oysters daily, there was a difference in the degree of calcification, but the difference was so slight that it was difficult to evaluate. It was not more than that induced by increasing the cod-liver oil 25 per cent. The poor results obtained in reproduction and rearing of young indicate that oysters contain but little vitamin E. The second generation males were impotent. The females produced some living young but had no capacity to rear them. The character of the diet may be questioned. However, results obtained with clams20prepared in the same way as the oysters, and similarly incorporated in the same diet are strikingly different. This strongly indicates that the poor results obtained with oysters with reference to reproduction and rearing of young are to be attributed to a specific deficiency in the oysters rather than to some other factor connected with the diet. 20
Unpublished data which will appear later.
Manganese in Steel and Pig Iron’ Volumetric Determination by the Vanadate Method Lawrence E. Stout and G. C. Whitaker C H E X I C A L LABORATORIES OF W A S H I N G T O N U N I V E R S I T Y , ST. LOUIS,
hfO., AND
X f I A M I UNIVERSITY, OXFORD, O H I O
The work reported herein presents (1) a method for sulfate in the presence of silHE potassium permanganate method for the the preparation of standard vanadyl sulfate solution ver nitrate. If the quantity determination of the from ammonium metavanadate; (2) a vanadate method of manganese in the sample vanadium content of an alloy for the determination of the manganese content of is small, the p e r m a n g a n i c steelisbaseduponthequantisteels and pig iron; (3) the effect of silver sulfate conacid is then d e t e r m i n e d centration on the rate of oxidation of manganese from c o l o r i m e t r i c a l l y . Larger t a t i v e r e d u c t i o n of t h e manganous nitrate to permanganic acid. quantities are determined by vanadium content from the titration against s t a n d a r d vanadate to the vanadyl condition and then its reoxidation by means of standard potas- sodium arsenite solution. Since in either case the manganese content of the steel sium permanganate.2 In determining the manganese content of a steel the Bureau of Standards official method3recommends is determined by the permanganic acid it can produce, the oxidation of the manganese content from manganous ni- and since the vanadium content of a steel is measured by trate to permanganic acid by means of sodium bismuthate, the amount of standard potassium permanganate required which is added in excess to the cold dilute nitric acid solu- to change the vanadium from the vanadyl to the vanadate tion of the steel. This quantity of permanganic acid is then state, it occurred to one of the writers that these two facts determined by filtering and adding a known quantity of might be combined to give a method for the determination ferrous sulfate, the excess of which is back-titrated with of the manganese content of steel and possibly pig iron, provided a standard solution of some reduced vanadium salt standard potassium permanganate. The ammonium persulfate method for the determination were available. of the manganese content of a steel provides for its quantiPreparation of Solutions tative oxidation to permanganic acid by ammonium perSTANDARD VANADYL SULFATE SOLUTION-TOprepare this 1 Received September 7, 1927. solution, 10 grams of ammonium metavanadate were dissolved 2 Scott, “Metallurgical Analysis,” p. 628. in 600 CC. of water and 40 cc. of 1:l sulfuric acid. An excess 8 I b i d . . p. 331.
T
INDUSTRIAL A N D ENGINEERING CHEMISTRY
February, 1928
of sulfurous acid solution was added and the mixture boiled for 20 minutes to drive off the excess sulfur dioxide. The solution was then cooled, diluted to 2330 cc., and standardized against a sample of steel the manganese content of which had been determined by the bismuthate method. One cubic centimeter of this solution was approximately equivalent to 0.1 per cent of manganese in a 0.200-gram sample. It is known that vanadium pentoxide is quantitatively reduced to the tetroxide by sulfur dioxide4and the reactions are probably as follows: 2NH4VOs
+ 2HzSOi v20a
+
&SO4
+
VzOs (NH4)zSO. excess &So4 soz -VzOa SOa excess
+ Hz0
+
Vanadyl sulfate solutions were found t o be the only ones of all those tried that are suitable for the titration. Vanadyl chloride solutions are unsuited for the purpose. When soluble chlorides are introduced into the solution the permanganic acid tends to interact with the evolution of chlorine. This reaction is not quantitative but was found sufficient to introduce considerable error. The vanadyl sulfate solutions were prepared from ammonium metavanadate because the salt was more readily available and cost less per gram of vanadium content. Standard vanadyl sulfate solutions possess a high degree of stability as contrasted with standard sodium arsenite solutions. Six months' standing failed to change the manganese equivalent of the solution. More extended work on this phase of the problem is now in progress. STOCKSODIUM CHLORIDESOLUTION4.3578 grams of c. P. sodium chloride were dissolved in water and diluted to 2000 cc. STOCKSILVER SULFATE SOLUTION-^^.^^^^ grams of silver nitrate were dissolved in 100 cc. of 10 per cent nitric acid, 40 cc. (1:1) sulfuric acid added, and the solution was boiled down to copious fumes of sulfur trioxide, then cooled and diluted to 2000 cc. These sodium chloride and silver sulfate solutions were made volumetrically equivalent, as the former is used to destroy the activity of the latter before the final titration. STOCKAMMONIUM I'ERSULFATE SoLuTIos-Ten per cent. Method for Steel Place 0.200 gram of steel in a 250-cc. Erlenmeyer flask and cover with 20 cc. of dilute sulfuric acid (1:3). Heat the flask and contents over a steam plate or low flame for 10 minutes without boiling, then increase the temperature until the liquid boils. When the sample has dissolved, add 5 cc. of stock ammonium persulfate solution and boil until it is decomposed. Cool the reaction mixture, add 10 cc. of stock silver sulfate solution, mix by shaking, then add 10 cc. of the stock ammonium persulfate solution. Allow the mixture to stand 30 minutes, then remove the silver ion by adding 10 cc. of stock sodium chloride solution, and titrate with standard vanadyl sulfate solution. The chemistry involved is probably as follows: The steel is dissolved in dilute sulfuric acid with the formation of ferrous and manganous sulfates. The former is probably oxidized by the next step to ferric sulfate, thereby being removed from the sphere of action. At the same time the manganous sulfate is quantitatively oxidized to permanganic acid by ammonium persulfate in the presence of silver sulfate: 2MnSO4
4
+ ~(NH~)zSO.S + 8Hz0 AgzSO4 --+ 5(NH4)&04 + 7Hz0 + 2HMn04
Scott, "Metallurgical Analysis," p. 628.
211
The excess of ammonium persulfate is rendered inert by removing the silver sulfate with sodium chloride as precipitated silver chloride. At this stage there is no material present to oxidize vanadyl compounds to vanadates except the permanganic acid. The quantity of the permanganic acid present is measured directly by titration with standard vanadyl sulfate solution. The titrating solution must be added very slowly (drop a t a time) as there is little warning of the approach of the end point. An overrun end point may be back-titrated if a standard potassium permanganate solution be available. Special Step for Analysis of Pig Irons I n the analysis of pig irons it is necessary to filter off the undissolved material (graphite) before the silver sulfate is added. From this point the procedure is the same as the one described above. Results Runs I to 20 were made after the method of analysis had been developed. The sample used was Government Standard 9C steel. The numbers on runs 21 to 56 were merely assigned to the samples by the director of the work and have no significance to the reader other than to indicate the number of determinations made upon each sample. Runs 21 to 56 illustrate the results obtained on a group of eleven samples of pig iron and steel, ten of which were commercial samples that had been analyzed by the bismuthate method, while one was a government standard issued by the Bureau of Standards. The analyst knew the correct manganese value of the steel used in runs 1 to 20. However, the manganese values on the samples used in runs 21 to 56 were known only to the director. The vanadyl sulfate solution was standardized against Bureau of Standards' sample 8C. Twenty titrations required an average of 5 cc. of vanadyl sulfate solution and corresponded to a manganese content of 0.446 per cent. Percentage calculations were then made by direct proportion RS follows : Run 1 5.0:7.5 = 0.446:~ x = 0.669 per cent Runs 51, 52, and 53 gave poor results because the standard
vanadyl sulfate solution was too strong. Better results Ivere obtained when larger samples were used, as in runs 54'55, and 56. It is possible that a less concentrated vanadyl sulfate solution might give more accurate results, but this point was not investigated because of lack of time. Table I-Determinations NATURE OF SAMPI,&"
of ManQanese in Steel a n d Pi& - Iron PERCENTMANGANESE VANADYL Vanadate Correct RUN SULFATE method value
cc. B. S. 9 C steel
No. 1B steel
No. 2B steel
11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
7.5 7.6 7.6 7.5 7.4 7.5 7.5 7.4 7.5 7.5 7.6 7.6 7.5 7.5 7.6 7.5 7.5 7.5 7.5 7.5 9.1 9.2 9.1 6.7 6.7 6.7
0.669 0.678 0.678 0.669 0.660 0.669 0.669 0.660 0.669 0.669 0.678 0.678 0.669 0.669 0.678 0,669 0.669 0.669 0.669 0.669 0.82 0.83 0.82 0.60 0.60 0.60
0.668b
0.80 0.60
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VOl. 20, No. 2
of Concentration and Time of Standing on Manganese Oxidation (Weight of samples, 0.6000 gram) STOCK AgaSOi VANADYL SULSOLUTION TIMEOF FATE SOLUTION M n USED STANDING USED OXIDIZED
Table 11-Effect
No. 3B pig iron
No. 4B steel No. 5B pig iron
No. 6B steel h'o. 7B steel
No. 8B steel
KO.10B steel h-0. 12B steel
27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
6.6 6.6 6.7 7.4 7.4 7.4 6.7 6.8 6.75 7.85 8.0 7.85 6.5 6.45 6.4 6.6 6.6 6.6
6.3 6.1 6.2 5.3 5.4 5.3
0.59 0.59 0.60 0.66 0.66 0.66 0.60 0.62 0.61 0.70 0.71 0.70 0.58 0.575 0.57 0.59 0.59 0.59 0.56 0.54 0.55 0.47 0.48 0.47
0.62
RUN 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76
0.65 0.62 0.70 0.57
0.60 0.64b
cc.
Minutes
cc.
5 5 5 5
30 60 120 180 30 60 120 180 30 60 120 180 30 60 120 180 30 60 120 180
25.1 25.1 25.1 25.1 25.0 25.1 25.1 25.1 25.0 25.1 25.1 26.1 24.9 25.0 25.1 25.1 22.2 23.6 24.4 24.5
1 1 1 1 0.5 0.5 0.5 0.5
Per cent 100 100 I00 100 99.6 100
100 100 99.6 100 100
100 99.2 99.6 100 100 88.45 94.02 97.2 97.6
0.462b
0.200-gram samples in all but runs 54, 55, and 56, where 1.000-gram samples were used. b These values are given by government analysis; others in this column were obtained by bismuthate method.
I n the first fifty-six runs (Table I) ample time and concentration of silver sulfate were desired to permit complete oxidation of the manganese to permanganic acid. It was also desired to know the minimum concentration of silver sulfate and the minimum time of standing that would permit 100 per cent oxidation. By varying the volume of the stock silver sulfate added (and of course using the correct volume of stock sodium chloride), a series of runs (57 to 76, Table 11) was made to determine the percentage of manganese oxidized in 30, 60, 120, and 180 minutes. All other conditions within the experiment were the same as before except that larger samples were used to make conditions more extreme.
It is noted that 30 minutes' standing is ample when 5 cc. of stock silver sulfate solution is used. Oxidation grows progressively less complete during this period of time when smaller volumes of stock solution have been added. If 1 hour's standing is permitted, the concentration of stock silver sulfate solution added may safely drop to 3 cc., but no lower. If 2 hours' standing is allowed, 1 cc. of the stock silver sulfate solution will answer the need. Even 3 hours' standing failed to effect complete oxidation when only 0.5 cc. of stock solution had been added. Conclusions
Standard vanadyl sulfate solutions prepared from ammonium metavanadate may be used to determine volumetrically the manganese content of a steel or pig iron. This vanadate method eliminates troublesome filtrations or unstable standard solutions required by other methods. The rate of oxidation of manganous sulfate to permanganic acid by ammonium persulfate in the presence of silver sulfate depends upon the concentration of the silver sulfate present in the solution.
Laboratory Cooling Device Using Liquid Sulfur Dioxide' A. F. Gill 178 QUEENST.,
customary "cold test" of castor oil for lubrication Ia tNaofTHE aircraft enginesa it is necessary to maintain the oil temperature of -10" C. for 10 days. An ice-salt mixture is specified as the cooling agent, and to insure a uniform temperature the tube containing the oil is jacketed with a vessel containing a potassium chloride solution with a freezing point of - 10" C. Such an apparatus requires more or less constant attention and frequent renewal of the cooling mixture. Under ordinary conditions the temperature rises considerably overnight. In a search for some means of cooling which would be suitable for a small laboratory lacking mechanical refrigeration, liquid sulfur dioxide was tried. As its boiling point is - 10 C., it was proposed to allow the liquid to boil slowly with the tube of oil immersed in it. This method was quite successful. Slow boiling wm maintained by keeping the liquid in a Dewar flask of about 5 cm. internal diameter. The castor oil to be tested was O
1
Received January 6, 1928.
British Engineering Standards, Assocn. Specification for Aircraft Materials, P. 8. 8
OTTAWA, CANADA
placed in an 18-mm. test tube as specified and with a thermometer running through the stopper to the bottom of the tube. The stopper was thickly coated with yaseline to exclude moisture and sulfur dioxide. When placed in the sulfur dioxide the oil varied in temperature by less than half a degree, the normal temperature being - 10.0" C. The only attention required was the addition of 100 cc. of sulfur dioxide every second day. The actual consumption of sulfur dioxide in 10 days was considerably under 500 cc. There was found to be no inconvenience from sulfur dioxide fumes when the material was kept in a fume cupboard. As the temperature was sufficiently constant no thermometer was needed in routipe use and the ends of the test tubes were sealed off in the flame. Rapid collection of liquid sulfur dioxide from the cylinders was accomplished by using the familiar spiral condenser surrounding a glass reservoir. Ice and salt could be used to cool this, but solid carbon dioxide and ether or gasoline are preferable. Care must be taken that the cold liquid attain its boiling point before putting it into the Dewar; otherwise it will stay supercooled for a considerable time and subject the oil to too low a temperature.
