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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
amount of standard titanium solution to t h e solution of non-titanium steel t o imitate the color of t h e test solution. If but two or three cc. are required, the amount used may be accepted as representing the amount in t h e test solution without further concern. But if more is required, t h e equality of volume of t h e two solutions, so vital t o accurate results, must be restored before final comparison. When colors match a t equal volumes, t h e amount of standard titanium solution used indicates t h e amount of titanium in t h e test sample. When t h e material analyzed is cast iron,’ t h e insoluble residue retains a small amount of titanium. For ordinary technical purposes this may be neglected. But if an accurate determination is desired, burn the insoluble in a platinum crucible, volatilize silica with hydrofluoric acid and 8 drops sulfuric acid (I : I), fuse residue with I gram sodium carbonate, dissolve out in dilute sulfuric acid and add t o t h e main solution. PROCEDURE FOR TITANIUM BELOW 0.02 P E R C E N T
The fact t h a t titanium does not alloy readily with iron often results in the production of a material in which titanium, though employed in the process of manufacture, exists in minute quantity. This circumstance led t h e writer t o cast about for some better means of determining these small amounts t h a n has heretofore been available. The method below requires about a n hour and a quarter, but is very useful when a report more satisfactory t h a n t h e conventional “trace” is desired. Weigh 2 grams of a non-titanium steel and the same quantity of the test sample. Place in dishes, a d d 50 cc. strong hydrochloric acid and heat t o complete solution. Add t o each 4 cc. nitric acid (sp. gr. 1.2) t o oxidize iron. Evaporate each solution t o about I O cc., pour into ‘separatory funnels, and wash the dishes with hydrochloric acid (2 parts strong acid, I part water). The total solution in the funnels should be in each case about 2 5 cc. Add cautiously t o each, 50 cc. ether (free of alcohol), shake under a hydrant, and allow t h e two solutions t o separate. Draw off the lower solutions into 400 cc. beakers, making the separation with care so t h a t not more than a drop of the ethereal solution passes into the beaker in either case. I t is essential t o conduct these ether separations with the twofold purpose of having t h e minimum amount of iron in the acid solutions and of having the iron content of the acid solutions nearly equal. Dilute each solution with 2 2 5 cc. hot water, add ammonia in slight excess, and boil. Allow the precipitates t o settle and filter through 1 1 cm. filter papers. Wash thoroughly with hot water to remove chlorides. Open t h e two filter papers into dishes, tearing off t h a t portion of the filter paper which holds no precipitate. Pour over each I O cc. of sulfuric acid (I : 3). Rock the dishes until the precipitate has all dissolved. Filter each into 3 0 cc. comparison tubes, using small funnels and 7 cm. filter papers. This filtration may be dispensed with, b u t it is best t o re1
Cast iron samples should be passed through a 60-mesh sieve.
Val. 5, No. g
move paper fiber. Wash the dishes and pass t h e washings through t h e filters. The total solution and washings in each instance should be equal in volume, between 1 5 and 18 cc. The solutions now have a light maroon color, depending on t h e amount of iron present. I n t o each tube introduce 3 cc. 3 per cent hydrogen peroxide and mix. T h e maroon color is discharged, leaving t h e solution practically colorless in the case of t h e non-titanium steel. But if the test solution contains t h e most minute quantity of titanium, its presence is revealed b y a residual lemon-yellow color. Even though t h e amount present is so extremely small t h a t the usual manner of comparison leaves the operator uncertain of its presence, a glance through the solution from t h e top, holding the tube about ‘/z inch above a white surface, instantly dispels all doubt. If there is as little as 0.001 per cent titanium present, t h e contrast between the pale green of t h e non-titanium solution and the yellowish tinge of t h e test clearly indicates t h a t fact. By adding t h e standard titanium solution t o t h e solution of non-titanium steel t h e percentage of titanium is readily determined. If the sample is cast i r o n , dissolve it in hydrochloric acid, filter and burn the residue in a platinum crucible. Volatilize silica with hydrofluoric acid and a few drops sulfuric acid, fuse residue with I gram sodium carbonate, dissolve out in hydrochloric acid, add t o t h e main solution, and proceed with the ether separation. The insoluble residue can not be neglected when material is being examined for small amounts of titanium. LIXALOCOMOTIVE CORPORATION LIMA,OHIO
VANADIUM IN STEEL BY THE HYDROGEN PEROXIDE COLOR METHOD B y C. R. MCCABE Received March 6, 1913,
I n 1 9 1 1 , the writer published the details of his original colorimetric method for vanadium in iron and steel’a method carefully devised to meet t h e difficulties occasioned by presence of titanium or molybdenum. Since these conditions are rarely encountered, a more direct and expeditious plan has been substituted for general use. It requires only twenty minutes when chromium is absent, and about double t h a t time when it is present. Results are entirely satisfactory, as many experiments have shown. The known rules governing all color methods are of unusual importance in t h e colorimetric vanadium determination. The large sample necessary renders the iron color deep enough t o influence the vanadium color very materially. The determination is further limited b y the sensitive character of t h e vanadium color with hydrogen peroxide, i t being affected by the acidity of t h e solution. With t h e strength of acids commonly used in analytical work, t h e acidity may be satisfactorily controlled b y means of t h e ordinary measuring apparatus. An excess of hydrogen peroxide partially bleaches t h e color after having pro1
Chem. Eng.. 18, 243.
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duced it. Also it is only when vanadium is in t h e quinquivalent state t h a t hydrogen peroxide imparts t o its solution a n immediate lasting color. It is impossible t o employ standard steels for t h e colorimetric vanadium determination with satisfactory results. For this reason t h e writer has devised a plan which consists in treating a non-vanadium steel precisely like t h e test, then imitating t h e color of t h e test b y addition of a standard vanadium solution t o the solution of non-vanadium steel, final comparison being made a t equal volumes. S T A S D A R D V A NA D I C JI S 0 L U T I 0 N
T h e vanadium pentoxide employed in making up the standard vanadium solution may be prepared in t h e laboratory, though it can now be obtained in t h e market. Select a good grade of vanadate of iron containing about 6 0 per cent VzOs, 3 8 per cent Fe203. and 2 per cent S i 0 2 ; p u t j grams of i t into a beaker, add I O O CC. strong hydrochloric acid, and heat until dissolved. Add 20 cc. water and I cc. hydrofluoric acid. Filter from t h e slight insoluble residue, using a large filter paper and ribbed funnel. Pour into a separatory funnel, add jo cc. ether, and shake under a hydrant. Allow t h e two layers t o separate completely. Draw off t h e acid solution into a beaker, and discard the ethereal solution. Continue the extraction until t h e solution is free of iron as shown b y the potassium sulfocyanide and ether test. Dilute t o 400 cc., filter into an 800 cc. beaker and pass air through t o remove the ether. Boil on a hot plate and add about I O grams of potassium chlorate t o oxidize t h e vanadium reduced by t h e hydrochloric acid. Then add in small quantities sufficient potassium carbonate t o neutralize t h e greater part of t h e acid. When t h e proper degree of acidity is reached, heavy precipitate of hydrated vanadic acid is thrown down. Filter through an 1 1 cm. filter paper, wash with hot water, and apply suction. Remove t h e cake, place on a watch glass and dry a t 100' C. Several hours may be necessary t o affect complete dehydration. Pulverize t h e v i nadium pentoxide a n d preserve in a vial. Place about 0.2 gram of the vanadium pentoxide in a small beaker. Add 3 0 cc. nitric acid (sp. gr. 1.2) and warm until dissolved. Dilute so t h a t I cc. contains 0 . 0 0 0 2 gram vanadium, or an amount corresponding t o a 0.01 per cent when a two-gram sample is taken for analysis. V A S A D I U M I S THE A B S E N C E O F CHROMIUM
Place 2 grams of t h e vanadium steel and t h e same quantity of a non-vanadium steel in 300 cc. Erlenmeyer flasks. Add exactly 40 cc. nitric acid (sp. gr. 1.2) t o each and heat until t h e steel is dissolved. T o each add about 0.1 gram potassium permanganate and digest for two minutes. Then add dilute ammonium bisulfite in sufficient quantity t o clarify t h e solution, and continue heating until SO2 is all expelled: b y this operation carbon is oxidized. Cool t h e solutions in running water and transfer to comparing tubes. Bring t o equal volumes if they are not already so. and mix. Observe t h e colors,
which should be of t h e same character and depth. I n t o each tube introduce exactly I cc. 3 per cent hydrogen peroxide. Mix the test solution, and observe t h e vanadium color t o gain an approximate idea of t h e vanadium content of t h e test. T o t h e solution of non-vanadium steel add, from a burette, as much of the standard vanadium solution as it is thought may be safely used without p x s i n g t h e amount existing in the test solution. T o the test solution add a n equal amount of water. Mix t h e solutions and compare colors. If t h e test solution appears darker, as will be the case if the proper precaution has been observed, add a further quantity of standard vanadium solution to t h e non-vanadium steel solution. Add an equal quantity of water t o t h e test solution t o maintain the equality of volume. Mix, and again compare. Continue in this manner until t h e colors match a t equal volumes. The amount of standard vanadium solution used indicates the result. Thus, if 2 0 . j cc. standard vanadium solution are used, the result is 0 . 2 0 j per cent vanadium. VANADIUM I N T H E P R E S E S C E O F CHROMIUM
When a vanadium steel contains chromium its color must be compensated t o secure a satisfactory comparison. The uncertain color of chromium salts, which varies with the acidity of the solution and other causes not readily determined, renders worthless some apparently simple methods of compensation. The only plan which proved satisfactory. after many experiments, is as follows: Weigh 2 grams of t h e chrome-vanadium steel and a n equal amount of a plain steel, placing in 400 cc. beakers. Weigh with great care a n amount of potassium bichromate corresponding t o t h e chromium content of t h e test steel and place i t in the beaker containing t h e plain steel. T o each add 80 cc. sulfuric acid ( I : 3 ) . and heat. When nearly in solution, add t o each 2 j cc. of strong nitric acid and heat for ten minutes. Vanadium is not completely oxidized b y a small amount of nitric acid such as would oxidize the iron. Cool the two solutions in running water, introduce into comparing tubes, and bring t o equal volumes. Mix, and observe the colors. Owing to possible error in t h e chromium determination i t is doubly important t o know t h a t t h e solutions show colors of the same character and depth a t equal volumes before proceeding with t h e analysis. The determination is now finished as when chromium is absent. For vanadium steels as they commonly occur, this method as described is entirely satisfactory. But when t h e determination is embarrassed by presence of titanium or molybdenum, or when t h e equally troublesome case of a steel containing a small amount of vanadium with much chromium presents itself, t h e more elaborate method mentioned in t h e first section of this paper may be employed. T h a t method, though i t requires more time, has been found t o be thoroughly reliable under adverse conditions. LIMA LOCOMOTIVE CORPORATION LIMA. OHIO
