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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 ENGINEERING CHEMISTRY
TABLEIV-COMPARISON
OF LEMONOIL DETERMINATIONS BY DIRECT WEIGHINGOF DISTILLEDO n A N D BY CALCULATION OF WEIGHT OF OIL PROM VOLUMEAND SPECIFIC GRATITYAT 25’/25’ C. Cc. Oil WEIGHTOF OIL LBS. OIL PER TON PER CENT OIL Direct from cc. Direct By No. Weight 200 g. X 0.846 Weight Calculation 637 . , . 0.69 1.73 1.464 13.8 14.6 639 ..... . . , 0.43 1.06 0.897 8.6 9.0 1.22 1.032 9.6 10.3 646 . . . . 0.48 662 ... , .. . . 0.66 1.64 1.387 13.2 13.9 1.438 675 . . 0.70 1.70 14.0 14.4 12.0 678 0.60 1.48 12.5 1.252 14.2 14.6 1.464 692.. , . 0.71 1.73 1.81 15.0 15.3 1.531 695..... . . . 0.75 1.36 10.8 11.5 1.151 696 . 0.54 1.44 11.0 12.2 1.218 706 ..... . 0.55 713.. .... . 0.42 1.09 8.4 9.2 0.922 717 ........ 0.57 1.40 11.4 11.8 1.184 1.11 9.0 0.939 0.45 9.4 726 ..... 1.46 11.6 12.4 1.235 806 0.58 10.4 1.23 1.041 9.8 826 , . 0.49 0.96 0.812 7.4 8.1 833 .. . , . 0.37 8.6 1.12 0.948 9.5 851.. . 0.43 1.00 0.846 7.6 8.5 880 0.38 12.0 1.42 1.201 11.6 883.. 0.58 10.1 915 . . 0.46 1.19 1.007 9.2 10.2 1.21 1.024 9.8 . . 0.49 920 1.303 12.4 13.0 1.54 921 0.62 10.3 1.22 1.032 9.4 955 ...... . . 0.47 1.15 0.973 9.0 9.7 957 . 0.45 0.99 8.0 8.4 0.838 998 . . 0.40
,.... .... ...... ....... .
.. . .
..... . .
. .. ... ....... . ...... ... .. . . . ........ ..... ...... ...... ........ ..... . . ......
of oil from t h e specific gravity, using t h e largest, smallest and average values for specific gravity, we have: 1.81 X 0,8511 X 0.996 = 15.34 lbs. per ton 1.81 X 0.8434 X 0.996 = 15.20 lbs. per ton 1.81 X 0.8490 X 0.996 15.31 lbs. per ton
-
The greatest difference is only 0.14 lb. per ton, which is well within t h e limits of experimental error. For determinations involving smaller volumes of oil t h e possible error involved through use of t h e factor is of course reduced. The yield of oil, pounds per ton, obtained by use of t h e factor is in every case a tri5e higher t h a n t h a t obtained by direct weighing. It is the intention t o continue the work and determine the specific gravities of t h e distilled oils of other California citrus fruit in order t o arrive a t a factor similar t o t h a t applied t o lemon oils. T h a t a n idea may be had of ‘the oil content of t h e fruit t h e d a t a already obtained is given.
THE DETERMINATION OF AVAILABLE OXYGEN IN PYROLUSITE By 0. L. BARNEBEY Received April 12, 1917
Pyrolusite is the principal manganese ore. The ore has value for t h e available oxygen and t h e manganese contained therein. Hence the determination of these two elements in t h e ore evaluate i t for the industries. Various methods for t h e determination of manganese have been studied by many chemists, but t h e methods in use for t h e determination of available oxygen have received but little attention.‘ Results for t h e percentage of manganese dioxide obtained by various responsible chemists have given differences of as much as five per cent on a carefully prepared sample, while differences of a per cent or two are quite common.2 This paper contains the results of a detailed study as t o t h e causes of such discrepancies and recommends two accurate methods for t h e analysis of oxidized manganese ores. Three methods have been in general use for t h e determination of available oxygen in pyrolusite: the oxalic acid m e t h ~ d ,the ~ ferrous sulfate method4 and t h e chlorine evolution m e t h ~ d . ~Of these methods t h e oxalic acid method is perhaps t h e most universally applied for this determination. Bunsen’s method is seldom used due t o t h e inconvenience of distilling the chlorine, which process becomes very time-consuming when a large number of ores are t o be analyzed. T H E OXALIC ACID M E T H O D
The oxalic acid method consists in dissolving a weighed portion of pyrolusite in a known quantity of oxalic acid in t h e presence of dilute sulfuric acid, heating t h e solution to facilitate reaction. The excess of oxalic acid is then titrated with standard permanganate and t h e per cent of manganese dioxide or TABLEV-PERCENTAGES OF OIL IN VALENCIAORANGES, TANGERINESavailable oxygen computed.‘j A N D GRAPEFRUIT BY DISTILLATION METHOD Any discrepancy existent in the analysis of an ore Cc. Oil Per cent Oil Sp. Gr. Direct of Oil dist. from should be evident when samples of t h e ore are anaNo. 200 g. Weight 25’/25’ C. lyzed under such conditions t h a t the factors involved Valencia Oranges(a) . . 999 1.80 0.71 0.8411 1001 1.77 0.70 0.8410 in the determination are alternately kept constant 1002 2.49 0.99 0.8411 1004 3.23 1.29 0.8424 and made variable. Thus one can maintain a conTangezises.. . . . . , . , . 835 1.35 0.52 0.8425 stant weight of sample, constant volume, constant .... 1.70 0.67 0.8388 .... 1.78 0.69 0.8418 amount of oxalic acid, constant temperature and make Grapefruit. . . . . . . . . . . 1361 0.79 0.30 0.8420 variable the sulfuric acid concentration. Two such (a) In a recent article by Hood [THIS JOURNAL. 8 (1916), 7091 data series of results’ are given in Table I. An approxare given on the oil content of Florida Valencias. Amounts were found not exceeding 0.53 per cent. This fruit wa9 peeled and the determinations made imately N / 4 oxalic acid solution was prepared and on the peel. In our experience, as above stated, t h i s practice invariably standardized from time t o time against standard yields l o w results. permanganate of approximately N / I Ostrength. The SUMMARY
I-The steam distillation method is t h e most practical one thus far developed for the determination of t h e volatile oil content of citrus fruit. 11-A special calibrated receiving flask has been designed t o meet t h e needs of this determination. 111-For rapid and reasonably accurate work t h e weight of t h e oil distilled from lemons may be calculated by multiplying t h e volume of t h e distilled oil a t 2j°C.b y 0 . 8 4 6 . Crrans BY-PRODUCTS LABORATORY BUREAUO F CHEMISTRY Los ANGELES.CAL.
1 See Bibliography of the Analytical Chemistry of Manganese, Talbot and Brown, Smithsonian Institution. Washington. D. C.. 1902. 2 See also Certificate of Analyses, Standard Sample Number 25, U. S. Bureau of Standards. a Hempel. “Neue Methoden zur Priifung des Braunsteins usw,” C. F. Winter. Heidelberg. 1843. 4 Originated by Levol. J . pharm. chim., (3) 1 (1842), 210; modified by Weldon and Lunge, Dingler’s Polytech. J.. 286, 300; 286, 231, 236; Chem. News, 41 (1880). 129, 141. 6 Bunsen, Ann. chim..86 (1853), 283. Fresenius and Will (Ann. chim., 47, 87; 49, 137; Dingler’s Polytech. J . . 90 (1843). 219) measure the COI produced. ’Samples 101, 102, 103, 104, 105, 106 were air-dried samples. received from The C. F. Burgess Laboratories. The samples had no tendency t o give up or take on moisture when being weighed for analysis. These samples were ground to pass 200 mesh silk bolting cloth and kept in glassstoppered weighing bottles.
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permanganate was standardized against pure sodium oxalate, ferrous ammonium sulfate and electrolytic iron. The volume of extraction solution was 2 0 0 cc. in this series. T h e temperature was maintained at about 7 5 until t h e residue was very light-colored and siliceous in character. After t h e ore had been completely dissolved t h e excess of oxalic acid was titrated with t h e permanganate. Samples 6, 7 and 8 were diluted with hot water before titration t o lessen t h e concentration of t h e sulfuric acid somewhat. Series I1 differed from Series I in t h a t t h e temperature was higher, being just below boiling. The results of Series I1 indicate t h a t better uniformity is obtained at t h e higher temperature, due t o t h e fact t h a t reaction occurs much more rapidly at t h e elevated temperature, thus diminishing t h e time necessary t o dissolve t h e ore. TABLE I-RESULTS Normality of Exp t. Sulfuric No. Acid 1 ......... 0.4 2 . . . . . . . . . 0.8 3. . . . . . . . . 1.6 4......... 2.4 5......... 3.2 6......... 4.0 i 8.0 8 12.0
.......... ........
O.S-GRAMWEIGHTSOF SAMPLES104 AND 105 -PERCENTAGES OBTAINEDSeries I-Sample 104 Serier 11-Sample 105 Available Manganese Available Manganese Oxygen Dioxide Oxygen Dioxide 14.09 76.58 13.18 71.45 70.49 13.90 75.50 12.97 13.92 75.65 12.92 70.17 75.05 12.91 70.15 13.81 13.76 74.83 70.15 12.91 74.80 70.02 13.77 12.89 74.59 69.92 13.73 12.87 73.44 13.51 12.84 69.78 , 0.58 3.14 0.34 1.67
ON
Maximum Difference.,. ,
.
X series of analyses was performed keeping t h e amount of sulfuric acid added constant and varying t h e volume, with t h e other factors t h e same as in t h e two previous series. The results were similar t o those tabulated in Table I , t h e lower t h e acid concentration t h e higher t h e per cent of manganese dioxide obtained. d n o t h e r series of experiments was performed varying t h e weight of samples taken for analysis. I n another series t h e amount of excess of oxalic acid was varied. I n still another series phosphoric acid was substituted for sulfuric acid. I n each series varying results were obtained. One of t h e most interesting features observed was t h a t as long as one maintains as nearly identical conditions of experimentation as possible t h e operator can usually obtain quite closely agreeing results. By changing conditions somewhat, again closely agreeing results are obtained, b u t these results are different from t h e previous series. This shows t h e method t o be highly empirical. T h e chemical nature of t h e reactions involved in this determination suggests several possible errors : I-Imperfect titration of oxalic acid t o carbonic acid; 11-Decomposition of oxalic acid during t h e heating period ; 111-Escape of oxygen during interaction of t h e pyrolusite and t h e oxalic acid; IV-Decomposition of t h e oxalic acid into water, carbon monoxide a n d carbon dioxide. These possibilities have been studied in t h e order named. I-TITRATION
OB OXALIC ACID B Y PERMANGANATE
Constant amounts of oxalic acid were titrated with permanganate. in constant volumes of solutions ( 2 0 0 cc.) containing variable concentrations of sulfuric acid a n d t h e solutions heated t o constant temperat u r e ( 8 5 " ) preceding titration (see Table 111).
Vol. 9, No.
IO
The conclusion from this series of experiments is t h a t oxalic acid can be titrated accurately in dilute hot sulfuric acid solution b u t when t h e hot solution becomes too concentrated in acidity a single drop of t h e permanganate in excess of t h a t required for t h e reaction with t h e oxalic acid will not give a recognizable tinge of color t o t h e solution. I n t h e concentration of sulfuric acid greater t h a n about 8 N , titrating a t 80°, t h e end-points are indistinct, t h e pink color imparted b y a drop of t h e standard permanganate fading very rapidly. With less t h a n 8 N acidity t h e end-points become more definite with diminishing acidity t o 0 . 8 N . The previous observation regarding acid concentrations explains t h e reason for t h e exceptionally low percentage of manganese dioxide obtained in E x p t . 8 of Series I a n d could easily account for a larger difference t h a n exists between Expts. 7 a n d S of Series 11. 11-DECOMPOSITION
OF OXALIC ACID I N HOT A Q U E O U S SOLUTION
It has been known for a long period of time t h a t oxalic acid decomposes slowly. A number of authors1-I6 have called attention t o this decomposition and have attributed t h e cause t o fungus growths, oxidation by t h e air, action of t h e light, molecular rearrangement, etc. Jorissen a n d R e i ~ h e r l ~studied ,'~ t h e r a t e of decomposition of oxalic acid in t h e presence of various substances over long periods of time (1-140 days) a t temperatures varying from room temperature t o 5 5 O. These authors conclude t h a t "the oxidation of oxalic acid is accelerated in diffused light in t h e presence of sulfuric acid, boric acid, sodium fluoride, sulfates of manganese, iron (ferrous a n d ferric), cerium (cerous and ceric), thorium, and erbium and also manganous acetate, butyrate, behzoate a n d oxalate. I n sunlight t h e acceleration increased with t h e amount of catalyzer added a n d was much greater t h a n in diffused light. T h e acceleration is dependent upon t h e composition of t h e catalyzer." They obtained decomposition effects as great as 4 . 6 per cent per d a y with manganous sulfate present. DeBries,' Lemoine,* and Lemoine and Poitevin3 found t h a t ferric salts in t h e light caused oxidation of oxalic acid. Unaware of Jorissen's work a t t h e lower temperatures, t h e author studied in a detailed manner t h e decomposition of oxalic acid a t a more elevated temperature and obtained some interesting results directly applicable t o t h e determination of available oxygen in pyrolusite. Wittstein, 2. anal. Chem., 1 (1862), 495. Neubauer. Ibid.. 9 (1870). 392. 8 Bizio, Ibid., 9 (1870). 52. 4 Downes and Blunt, Chem. News, 36 (1877), 279; Jahrcsb.. 1870, 643; C. C . 1870, 50. 6 Richardson. J . Chem. Soc., 66 (1894), 450. 453. 6 Hartley, Chem. News, 37 (1878). 9. 7 Fleury, J . Pharm. Chem.. [SI 7 , 388. 8 DuClaux, Compt. rend., 103 (1886), 1011. 9 Warburg, Untersuch. botan. Inst. Tubingen, 2 (1886-8), 117. 10 Wehmer. Bot. Zlg., 1891, 41. 11 Gigli. C . C.. 1 (1893), 1 1 . Gerland, J . Soc. Chem. I n d . , 10 (1891j, 25. 18 Reigler, 2. anal. Chem., 35 (18961, 522. $4 Jorissen, 2. angew. Chem.. 1899, 521. 16 Jorissen and Reicher. 2. p h y s . Chem., 31 (1899), 142. 1
2
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TABLE
11-ACCURACYOF PERMANGANATE T I T R A T I O N O F O X A L I C ACID h'ORMALITY GRAMS E X P . Sulfuric OXALICACID No. 1 la 2 2a 3 4
5 50 6 7 8 9
Acid 0.8 0.8 1.6 1.6 4.0 6.0 8.0 8.0 10.0 12.0 18.0 28.0
Present 0.2504 0.2504 0.2504 0.2504 0.2504 0.2504 0.2504 0.2504 0.2504 0.2504 0.2504 0.2504
Found 0,2504 0.2503 0.2503 0.2505 0.2503 0.2505 0.2506 0.2505 0.2510*
** ** **
* End-point rather indefinite. ** End-point very indefinite.
963
TABLE 111-DECOMPOSITION OF (1) E f e c t of Heating with HzS04
NORMALITYGRAMS Sulfuric OXALICACID
EXP.
No. 1 2 3 4 5 6 7 8 l: 11 12 13 14 15
Acid 0.4 0.8 1.6 2.4 3.2 4.0 8.0 2.4
Present 0.2502 0.2502 0.2502 0.2502 0.2502 0.2502 0.2502 0.2502
;:: i:;;::
2.4 2.4 2.4 2.4 2.4
Found 0.2504 0.2498 0.2497 0.2504 0.2503 0.2503 0.2504 0.2503
0.2502 0.2503 0.3336 0.3333 0.5004 0.4996 0.6672 0 . 6 6 5 4 0.8340 0.8324
O X A L I C ACID I N HOT AQUEOUS S O L U T I O N (2) Efect of Manganous Sulfate (3) Efect of Sunlight NORMALITY OF GRAMS NORMALITY OF GRAMS EXP.Sulfuric Manganese OXALICACID E X P . Sulfuric Manganese OXALICACID No. Acid Sulfate Present Found No. Acid Sulfate Present Found 1 2.4 0.02 0.2502 0.2459 1 0.02 2.4 0 . 2 1 8 4 0.1973 2 0 . 0 4 2 . 4 0 . 2 1 8 4 0.1970 2.4 0.04 0.2502 0.2433 3 0.06 2.4 0 . 2 1 8 4 0.1951 2.4 0.06 0.2502 0.2337 3 4 2.4 0.10 0 . 2 1 8 4 0.1965 5 2.4 0.20 0.2184 0.1956 2.4 0.10 0.2502 0.2321 6 0.40 2.4 0.2184 0.1967 2.4 0.2502 0.2301 0.20 5 7 0.00 2.4 0 . 2 1 8 4 0.2155 8 0 . 0 0 . 0 0 0 . 2 1 8 4 0.2175 6 2.4 0.2502 0 . 2 3 1 0 0.40 0.8 0.06 9 0 . 2 1 8 4 0.1994 7 0.2502 0.2280 10 0.80 2.4 0.06 1.6 0.2184 0.1994 0.06 2.4 0.2184 0.1995 2.4 0.2502 0.2263 1 1 1.20 8 12 0.06 3.2 0.2184 0.2008 g 2.4 0.2502 0.2327 13 1.60 0.06 4.0 0 . 2 1 8 4 0,2027 0 . 0 6 0 . 0 14 0.2184 0.2104 2.4 2.00 0.2502 0.2292 lo 2.4 0.20 15 0.2502 0.2177 2.4 11 . . . . 0.2502 0.2502 16 2 . 4 0 . 2 0 0.2502 0.2124
( I ) T h e effect of heating oxalic acid solution with varying a n d constant concentrations of sulfuric acid in diffused daylight was studied. Constant portions of standard oxalic acid were measured into beakers a n d 16 N sulfuric acid added in varying amounts followed b y sufficient water t o make 2 0 0 cc. in each case. The solutions were then heated for six hours a t 85' in diffused light, after which t h e oxalic acid was titrated with standard permanganate [see Table I11 (I)]. I n Expts. 8 and 9 the oxalic acid was titrated as soon as t h e solutions h a d reached 80' a n d these titrations served as a standard with which t o compare t h e other titrations. I n Expts. I O t o 1 5 t h e normality of t h e sulfuric acid was maintained constant and t h e oxalic acid concentration progressively increased. I n these last five experiments t h e heating period was 4 hours a n d in t h e first seven experiments 6 hours. This series shows t h a t t h e loss occasioned b y heating in diffused sunlight oxalic acid solutions acidified with dilute sulfuric acid is very slight indeed, in fact negligible over t h e short periods of time when application t o analytical' chemistry is considered. ( 2 ) The effect of t h e addition of t h e products of reaction in t h e determinations was then studied. Potassium sulfate a n d acid sulfate were found t o have no particular influence. LIanganous sulfate, however, exerted a striking effect. I n consequence of this effect a more detailed s t u d y was taken u p with t h e manganese, typical results being quoted in Table I11 ( 2 ) . I n this series of experiments t h e volume was 2 0 0 cc. a n d t h e heating period was 4 hours a t a temperature of about 80". A 4 N manganese sulfate solution was used as t h e source of t h e manganese. Table I11 ( 2 ) shows manganese sulfate t o have a tendency t o accelerate t h e decomposition of oxalic acid very markedly. I n general, t h e above series of results indicates t h a t the decomposition increases as t h e amount of manganese increases. I n Expts. 7, 8, 9 a n d I O difficulty was experienced in obtaining a n end-point due t o t h e pink coloration imparted t o t h e solution by t h e rather large amounts of manganese sulfate. Another series of I j experiments was performed under similar conditions t o those of Table I11 ( 2 ) except t h a t t h e concentration of manganese sulfate was kept constant, 0.06 N , and t h e sulfuric acid concentration was varied from 0 . 4 N t o 12.0 N . I n all cases there was decomposition of t h e oxalic acid
during t h e heating period, t h e results showing somewhat irregularly from 4 t o 8 per cent loss of oxalic acid. I n t h e previous series t h e experiments were performed in beakers covered with watch glasses. A series of experiments was performed using Erlenmeyer flasks fitted with Bunsen valves, t h u s allowing t h e steam t o displace t h e air in t h e flask. T h e decomposition of t h e oxalic acid proceeded in t h e same general manner as before only t o a lesser degree. Other series were performed with flasks fitted with Bunsen valves, removing t h e air b y carbon dioxide before fitting on t h e valve. This method of procedure diminished t h e decomposition b u t did not completely prevent it. T o remove t h e source of difficulty, t h e effect of boiling was also tried, with results similar t o those obtained by use of carbon dioxide. (3) I n some preliminary experiments sunlight was found greatly t o accelerate t h e decomposition of oxalic acid. These experiments were followed by a systematic study of t h e light effect. Table I11 (3) contains t h e results of heating in direct sunlight oxalic acid solutions containing variable amounts of manganese sulfate. The concentrations of oxalic acid, sulfuric acid, t h e volume ( 2 0 0 cc.) and t h e temperature (90") were kept constant in Expts. 1-7, inclusive. I n Expts. 9-13, inclusive, t h e manganese sulfate was maintained constant with t h e other factors a n d t h e acidity made t h e variable. Expts. 1-8, 9-14, and 15-16 were performed on three different days. The sunlight was quite strong on t h e first two days a n d very bright on t h e third day. The time of heating in the sunlight was 3 hours in every case. I n Expts. 1-6 a somewhat constant loss occurredapproximately I O per cent of t h e oxalic acid. With no manganese sulfate present ( 7 ) t h e decomposition was much less a n d also with no sulfuric acid present (8) t h e loss was still less than in the previous cases. Increase in acidity in Expts. 9-13 gave a gradually increased preservation of t h e oxalic acid although a t no time was t h e loss small in amount. With no sulfuric acid present (8 and 14) t h e decomposition was not quite as large as when i t was present. However, more experimentation should be carried out t o prove this point definitely. Experiments I j a n d 16 were conducted over 4-hour periods instead of 3 in very bright sunlight. I n Expt. 1 5 t h e solution
GINEERING C was contained in a n Erlenmeyer flask closed with a Bunsen valve a n d 16 was contained in a beaker covered with a watch glass. It is t o be noted t h a t in Expt. 16 thc percentage loss during t h e hcating period attained over 15 per cent. This work proves definitely t h a t manganese sulfate in t h e presence of t h e light a t a temperature of So-90' causes oxalic acid in sulfuric acid solution t o decompose rapidly. In this s t u d y of t h e decomposition of oxalic acid t h e time intervals were made 3 t o 4 hours in order to give greater accuracy t o the work than a shorter time would give. Only occasionally will such a length of time h e required t o dissolve a pyrolusite ore sample provided t h e ore is pulverized t o pass a abo-mesh silk bolting cloth. When t h e ore samples are passed through a loo-mesh sieve or less such a length of time for t h e decomposition using a temperature of 8 o o will frequently be necessary. If t h e solution is heated t o boiling, t h e time is greatly reduced. If t h e time of heatin.g can be diminished, a s i n t h e case of some ores, to a few minutes a n d t h e operation be conducted i n diffused daylight, or still better in t h e dark, especially if conducted in a n atmosphere free from oxygen, t h e error due t o decomposition of oxalic acid in t h e determination of available oxygen in pyrolusite is reduced t o a minimum. However, so great is t h e decomposition of oxalic acid in hot sulfuric acid solutions containing bivalent manganese t h a t no exact analytical method can h e formulated without preventing this decomposition effect. Inasmuch a s bivalent manganese is a n end-product in' t h e determination of available oxygen in pyrolusite t h e task of preventing t h e effect is a dificult one. All attempts t o counteract t h e decomposition completely have t h u s f a r failed. There is another possible cause for t h e decomposition of oxalic acid in solution and t h a t is t h e possibility of oxalic acid undergoing rearrangement or decomposition, or both, forming other organic compounds which are not titratable with permanganate t o t h e extent of t h e full equivalent original oxalic acid. This point h a s not been investigated. 111-ESCAPE OF O X Y G E N DURING I N T E R A C T I O N O F MANGANESE nioxInE A N D OXALIC ACID
T h e possibility suggested itself t h a t oxygen may he evolved in small amounts when manganese dioxide and oxalic acid react in sulfuric acid solution. T h e probability of such a n effect seemed all t h e more plausible in t h e light of t h e experiments of Richardson,L who calls attention t o t h e formation of hydrogen peroxide when oxalic acid decomposes. T o test t h e above point t h e following experiments were performed: 50 grams of manganese dioxide suspended in 2 . 5 liters of pure water were placed i n a 3-liter balloon Bask. The water was prepared by distilling, first from alkaline permanganate, then from potassium acid sulfate. A reflux condenser was attached 'LOG. 'il.
ISTRY
Vol 9, N o
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t o t h e flask, a n d t o t h e condenser was attached a U-tuhe containing ammoniacal manganese chloride solution. The U-tube was protected from a second U-tube likewise containing a manganese chloride solution. The suspension was heated t o boiling for some time t o insure as complete removal of air from t h e system as possible; then t h e U-tubes were connected and t h e heat continued t prove a negat.ive effect of manganese dioxide d o n Then 80 g. of oxalic acid contained in I : 4 sulfuric acid, previously hoiled t o remove any dissolved air, were added through a separatory funnel fitted through a second hole in t h e rubber stopper which makes t h e connection between t h e flask and t h e condenser. Boiling was continued for some time but no appreciable oxidation of t h e manganese t o manganese dioxide occurred in t h e test U-tube. Cuprous chloride was also employed with similar results. IY-DECOMPOSITION OF OXALIC ACID m r o WATER, CARBON MONOXIDE A m C A R B O N DIOXIDE
Any direct decomposition of oxalic acid sult in t h e formation of carbon monoxide, oxide a n d water. If t h e decomposition reac t o oxidation only then no carbon monoxide would be found a s a n end-product of t h e reaction. To ascertain if any carbon monoxide is formed by heating dilute sulfuric acid solutions of oxalic acid a number of experiments were performed. A solution of So g. of crystallized oxalic acid in two liters of I . 5 N sulfuric acid
Frc. I
a reflux condenser, b , containing a t r a p , c, which returned any water carried over mechanically back t o t h c Bask a through t h e t u b e d The tube c conducted t h e gas t o t h e wash bottle f , which contained concentrated sulfuric acid which removed t h e water f r o m t h e gas. The gas t h e n entered t h e t u b e g which contained a charge of LOs which completely filled 8 in. of t h e t u h e h. T h e I p O iwas prepared from HIOa b y dehydration a t 160". Plugs of glass wool were inserted i n t h e t u b e to support t h e iodine pentoxide a n d also to act as filters for t h e gas The second plug was t a rather snugly t o prevent a n y of t h e pentoxide. T h e pen at 1 3 o t o 1 3 5 ~ b y t h e c a r h o n e
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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
b a t h k . The gas passed from g t o t h e suction flask I which contained a dilute solution of KOH. The suction flask was connected t o a suction pump by means of the t u b e m.; n is a tower filled with soda lime and o is a U-tube half filled with glass wool. The solution was heated by means of the electric hot plate and t h e gases formed by the decomposition removed by drawing air through t h e system a t t h e r a t e of about 5 liters per hour. The gas passed through t h e heated iodine pentoxide. Any carbon monoxide present in the gas then reacted with t h e pentoxide, liberating iodine which was absorbed in the potassium hydroxide. A t t h e end of t h e decomposition period t h e potassium hydroxide solution was made distinctly acid with hydrochloric acid, potassium iodide added, then the iodine titrated with 0.I N thiosulfate (see Table IV). TABLEIV-DECOMPOSITION O F OXALIC ACID AT 90-95‘ c. Total cc. cc. EXP. Time 0.1 N NazSzOa No. LIGHT Hrs. Nad320a required per hr. 0.14 1 Diffused Sunlight.. . . . . . . . . . . . . . . 4 0.56 2 Darkness ....................... 12 1.20 0.10 3 Direct Sunlight.. . . . . . . . . . . . . . . . 4 0.68 0.17 Added 100 cc. of 4 N MnSOd 5 0.36 0.07 4 Diffused Sunlight.. 5 Darkness 17 1.10 0.06 4 0.60 0.12 6 Direct Sunlight.. With pure water in Flask a 0.00 7 Diffused Sunlight.. 4 0.00 0.00 8 Direct Sunlight.. 4 0.00
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The results of Table VI1 show t h a t very small amounts of carbon monoxide are continuously evolved from heated I . 5 N sulfuric acid solutions of oxalic acid. Expts. I , 2 and 3 performed without t h e a d dition of manganese gave more carbon monoxide t h a n did Expts. 4, 5 and 6, which contained manganese sulfate. This indicates t h a t t h e manganese facilitates t h e oxidation of carbon monoxide by the air before i t is evolved from t h e solution. Expts. 7 and 8 were performed as blanks on t h e effectiveness of t h e apparatus and t o determine what, if any, amount of decomposition of t h e iodine pentoxide was caused by ’ t h e heat alone in t h e intervals of time of experimentation. The results showed no decomposition in the absence of oxalic acid from Flask a. These experiments prove t h a t only very slight amounts of carbon monQxide are evolved by heating oxalic acid in dilute sulfuric acid solution. Hence t h e major portion of the decomposition of t h e oxalic acid in such solutions is undoubtedly t h a t of air oxidation of the oxalic acid in t h e heated solution, t h e manganese sulfate acting as a carrier and t h e light accelerating this action. THE FERROUS S U L F A T E METHOD
The ferrous sulfate method, like t h e , oxalic acid method, has been in use for a long time a n d is described in many of our text-books1 dealing with quantitative analysis. I n brief, the method now used consists in dissolving t h e pyrolusite in an excess of ferrous sulfate or ferrous ammonium sulfate in t h e presence of sulfuric acid, and after t h e ore is completely decomposed the excess of ferrous iron is titrated with permanganate. 1 Treadwell-Hall.
“Analytical Chemistry,” Vol. 11. 1911, Ed., p. 624.
Olsen, “Quantitative Analysis.” 1916 Ed., p. 326.
96 5
Manganese salts have been shown by the author’ t o act as oxygen carriers between the air and ferrous salts in fluoride solutions, but in sulfate solutions no such effect was obtained, a t least the effect was found t o be so small t h a t it was negligible during a moderate period of time. However, the study was conducted in diffused daylight. I n order t o ascertain if any effect of this kind is caused in sulfuric acid solutions in the presence of direct sunlight t h e experiments of Table V were performed. Sample 8 was titrated TABLEV-EFFECT OF DIRECTSUNLIGHT AND MANGANESE SULFATE ON THE OXIDATION OF FERROUS SULFATE IN SULFURIC ACID SOLUTION Experiment Normality of No. HiSOi 1 ................ 2 . 4 2. . . . . . . . . . . . . . . . 2 . 4 2.4 3... 2.4 4 5 2.4 2.4 6 7 2.4 8 2.4
.............
................ ................ ................ ................ ................
Normality of MnSOi 0.20 0.40 0.20 0.15 0.10 0.05 0.00 0.00
GRAMS IRON Taken Found 0.5301 0.5301 0.5301 0.5301 0.5301 0,5301 0.5301 0.5301
immediately without heating. Samples 1-7, inclusive, were contained in a volume of 2 0 0 cc. and were heated t o about 80’ in the direct sunlight for 4 hours. The solutions in I , 2 and 6 were contained in beakers covered with watch glasses, and 3, 4, 5 a n d 7 were contained in Erlenmeyer flasks likewise covered with watch glasses. This series shows conclusively t h a t t h e oxidation due t o atmospheric oxygen must be very slight indeed in solutions sufficiently acid with sulfuric acid. The effect of pulling air b y suction through solutions similar t o those of Table VI11 heated t o about 80’ was studied. These experiments were performed in diffused daylight. The solutions were contained in Erlenmeyer flasks and were heated by an electric hot plate. Sample 4 was titrated immediately. The TABLEVI-EFFECT
OF PASSING A CURRENT OF AIR THROUGH FERROUS SULFATESOLUTIONS CONTAINING MANGANOUS SULFATE
Experiment Normality No. HaSOi 1 0.8 0.8 2 3 .......... 0 . 8 0.8 4
.......... .......... ..........
Normality MnS04 0.2 0.2 0.0
0.0
Time Hrs. 2 3 3
..
GRAMSIRON Taken Found 0.5301 0,5290 0.5301 0.5300 0.5301 0.5298 0.5301 0.5300
results of Table I1 show t h a t manganese sulfate does not materially increase t h e rate of oxidation of ferrous sulfate by t h e oxygen of t h e air in solutions sufficiently acid with sulfuric acid. The fact t h a t ferrous sulfate solutions are far more stable in t h e presence of manganese salts t h a n are oxalic acid solutions, especially when sunlight is involved, suggests t h e elimination of oxalic acid and t h e substitution of ferrous sulfate in all possible cases involving t h e presence of manganese sulfate or sunlight where a period of time of heating is involved. T o ascertain what errors, if any, are inherent in t h e ferrous sulfate method, several series of experiments were performed along t h e same general lines as those involved in t h e study of t h e oxalic acid method. I n Table VI1 are given t h e results obtained with 0 . 5 g. samples of pyrolusite. The ferrous sulfate solution contained 600 g. of crystallized ferrous sulfate and IOO cc. of sulfuric acid (sp. gr. 1.84) in 8 liters. The solution was accurately standardized previous t o use withfpermanganate which was stand1
J . A m . Cham. Soc..37 (1915). 1481.
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 C H E M I S T R Y ardized against electrolytic iron and ferrous ammonium sulfate: 50 cc. of t h e ferrous sulfate were originally added t o t h e sample contained in a n Erlenmeyer flask followed by t h e sulfuric acid and t h e manganese sulfate, if a n y of t h e last named salt was added. T h e flask was t h e n covered with a watch glass and heated. The flask was occasionally agitated t o facilitate solution of t h e ore. When decomposition was complete each solution was diluted somewhat with water and t h e cooled solution titrated with permanganate t o determine t h e excess of ferrous sulfate. TABLE VII-ANALY SIS OF PYROLUSITE FOR MnOz CONTENTBY FeSOc METHOD Experiment Normality Normality Per cent MnOi MnSO4 added Found No. His04 1 ..................... 0.0 0.0 70.72 2 ..................... 0.4 0.0 70.40 3 . .................... 0.8 0.0 70.45 70.32 4 2.4 0.0 0.0 70.30 4.0 5 0.0 6 . . . . . ................ 8 . 0 70.18 i . . . . .... . . . . . . . . . . . . . 0 . 8 0.2 70.20 8 1.6 0.2 70.18 70.10 9 ..................... 4.0 0.2 10 0.8 0.0 70.18 11 1.6 0.0 70.20
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Expt. I (and also z a n d 3 t o a lesser degree) gave a high result due in all probability t o a n insufficient quantity of sulfuric acid t o prevent t h e ferrous sulfate from oxidizing. Only t h e sulfuric acid contained in t h e j o cc. of standard ferrous iron solution was present in t h e experiment. The endpoints of Expts. 6 , 7, 8 a n d 9 were somewhat indistinct. Greater dilution, t h u s diminishing t h e manganese concentration in 7 , 8 and g a n d of sulfuric acid in 6, would have made t h e end-points clearer. The results from 4 t o 1 1 , inclusive, show a good agreement under different solution conditions, which is not t h e case with t h e use of oxalic acid solutions. Other samples were analyzed under t h e same conditions as those given in t h e preceding series t o test t h e general application of t h e procedure. Some typical results are given in Table VI11 along with results obtained b y t h e direct iodimetric and chlorine distillation methods on t h e same samples. Hence this series gives not only a test as t o t h e accuracy of t h e ferrous sulfate method b u t a comparison of t h e three methods as well. TABLE VIII-COMPARATIVERESULTS OF FERROUSSULFATE,DIRECT AND DISTILLATIOW METHODS IODIMETRIC PER CENT MnOz FOUND Ferrous Direct Chlorine Normality Sulfate Iodimetric Distillation Sample No. His04 Method Method Method 69.60 69.87 101 0.8 69.68 69.70 1.6 101 ..... ..... 2.4 101 80.10 80.10 0.8 102 80.04 80.20 1.6 102 ..... ..... 102. ............ 2 . 4 85.00 84.90 0.8 103 84.83 84.80 84.92 103 1.6 ..... ..... 84.83 103 2.4 75.04 75.17 75.22 1.6 104 75.20 75.20 75.30 104 .............. 2 . 4 70.40 70.18 70.44 0.8 105 70.36 70.32 70.47 105 . . . . . . . . . . . . . 1 . 6 ..... ..... 70.44 105 2.4 78.32 78.20 78.20 106 ............. 1 . 6 78.18 78.28 78.20 106 ............. 2 . 4
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I n Table VI11 t h e column “Ferrous Sulfate Method” contains t h e results obtained b y t h e ferrous sulfate method as previously outlined. The column “Direct Iodimetric Method” contains t h e percentage obtained by use of t h e author’s direct iodimetric method.’ 3
J . A m . Chcm. SOC.,89 (1917), 607.
Vol. 9, No.
IO
I n t h e column “Chlorine Distillation Method” are contained t h e results obtained b y Bunsen’s distillation method.’ The results show a very good agreement among t h e three methods. The following outline is recommended for the analysis of pyrolusite by t h e ferrous sulfate method. PREPARATION OF SOLUTIONS
The following d a t a are calculated per liter of each solution b u t t h e solutions are best made u p in large volumes. F E R R O U S S U L F A T E SOLUTION-200 cc. of sulfuric acid (sp. gr. 1 . 8 4 ) are slowly added t o 900 cc. water with stirring and while t h e solution is still warm 90 grams of crystallized ferrous sulfate (FeS04.7HzO) are added, stirring until solution is effected. The solution should be a t room temperature before use. This solution is standardized just preceding use against t h e standard solution of permanganate. P E R M A N G A N A T E SOLUTION-IO g. of permanganate are dissolved per liter of water a n d t h e solution allowed t o s t a n d several weeks before use. This solution is approximately of t h e same equivalent strength as t h e ferrous sulfate solution prepared as above. The permanganate is standardized b y means of any reliable standardizing agent, such as electrolytic iron, ferrous ammonium sulfate or sodium oxalate. PROCEDURE
A sufficient quantity of t h e well mixed sample is ground t o pass a 200-mesh seive a n d dried a t IOOSome samples when dried Iojo t o constant weight. in this. manner have a tendency. t o take on water during weighing and consequently such samples should be weighed by difference from a glass-stoppered weighing bottle. Other samples do not have this tendency and may be weighed directly o n a watch glass. A 0 .j gm. sample is placed in a z jo cc. Erlenmeyer flask: jo cc. of t h e standard ferrous sulfate solution are added, t h e flask is covered with a watch glass a n d t h e solution heated t o boiling until solutiori of t h e ore is accomplished. The solution is then diluted t o about Ijo cc. a n d t h e excess of ferrous iron titrated with standard permanganate. I n consequence of t h e preceding work t h e ferrous sulfate a n d direct iodimetric methods are t o be recommended for t h e analysis of pyrolusite for its available oxygen or manganese dioxide content. I n t h e laboratory, which requires a large number of determinations each day, t h e ferrous sulfate method will be found most appropriate as t h e use of a n y iodimetric method will be found expensive, due t o the present cost of iodides. Where a smaller number of analyses are t o be made either method will be found applicable. CONCLUSIONS
I-The oxalic acid method for t h e determinatidn of available oxygen in pyrolusite has been found t o be inaccurate.
‘ LOG. crt.
OCt.,
1917
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 C H E M I S T R Y
11-The inaccuracy is due t o t h e decomposition of t h e oxalic acid during t h e heating period required for t h e solution of t h e ore. 111-Manganese salts a n d t h e sunlight greatly accelerate t h e decomposition of oxalic acid. IV-Some carbon monoxide is evolved from dilute sulfuric acid solutions ( I . 5 N ) containing oxalic acid, b u t t h e amount of this decomposition is very small. V-No appreciable quantity of oxygen is evolved when manganese dioxide a n d oxalic acid react in dilute sulfuric acid solution. VI-The ferrous sulfate method is not subject t o t h e errors of t h e oxalic acid method enumerated in I, I1 and 111. VII-The ferrous sulfate and t h e direct iodimetric metliods are t o be recommended for t h e determination of t h e available oxygen in pyrolusite. This investigation was carried out for and in COoperation with t h e C. F. Burgess Laboratories of Madison, Wisconsin, and i t is with their approval t h a t t h e foregoing publication is made. MADISON,WISCONSIN ~-
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A CONTRIBUTION T O THE THEORY OF EMULSIFICATION BASED ON PHARMACEUTICAL PRACTICE-11’ By WILLIAMG. CROCKETT AND RALPH E. OESPER Received June 12, 1917
In a previous article* t h e existence of “critical points” of emulsification was pointed out. Depending on t h e method of determination, these critical values have been defined as either ( a ) t h e minimum quantity of emulsifying agent, say acacia, t h a t can produce permanent emulsification of a given quantity of oil in a fixed quantity of water, or, ( b ) t h e minimum quantity of water t h a t can bring about stable emulsification of a definite quantity of oil by a fixed quantity of emulsifier, say soap. Given standard conditions, these points are quite definite, for while permanent emulsions are produced b y these critical amounts, t h e use of a few milligrams less of emulsifier or of a small fraction of a cubic centimeter of water less t h a n these quantities results in imperfect, temporary emulsification or none a t all. Although quantities in excess of t h e critical value do bring about emulsification, t h e resulting emulsions do not possess t h e stability or general excellence of those prepared from t h e critical proportions. T h e character of t h e emulsion depends in no small degree upon t h e procedure followed in its preparation a n d i t was found t h a t t h e emulsifier is most efficiently used when it is hydrated all a t one time and in t h e presence of t h e internal phase. This work has been extended t o other systems whose critical points have been determined a n d t h e conclusions drawn from our previous experiments have been supported by these later results. It was found t h a t t h e size and shape of t h e vessel in which t h e emulsion is prepared has a distinct influence on 1 The work reported in this article constitutes the basis of a thesis submitted by William H Crockett to the Faculty of the Graduate School of New York University in part fulfillment of the requirements for the degree of Master of Science. 2 Roon and Oesper, THIS JOURNAL, 9 (1917), 156.
96 7
t h e critical point a n d a n extended s t u d y of this factor which probably involves a consideration of viscosity, surface tension, etc., is planned. A preliminary report of t h e combined influence of several emulsifiers on t h e critical point is included. EXPERIMENTAL
PHASES MATERIALS USEDAS INTERNAL 1-Carbon tetrachloride, 4-Oil of Turpentine, U. S. P., sp. gr. 0.86. B. P. 76.4-76.8’. 5-Oil of Almonds, expressed, 2-Chloroform, U. S. P.. sp. gr. 0.912. B. P. 61.3-61.8’. 6-Mineral Oil. sp. gr. 0.853. 3-Benzene. B. P. 80’. Nos. 1, 2 and 3 were dried over calcium chloride for 18 hrs. and fractionally distilled. EMULSIRIERS USED I-Powdered acacia. 2-Powdered tragacanth. 3-Extract of Irish moss; prepared by boiling the moss with water, straining and evaporating the filtrate to dryness. The residue was then rubbed to a fine powder in a mortar. &Soft soap, Squibb’s; alcoholic solution, containing 25 g. in sufficient alcohol to measure 50 cc. TABLEI-TRAGACANTHEMULSIONS Size of INTERXAL MIXTURETragacanth Globules CRITICAL iYo. Gram Microns EMULSION POINT PHASE Chloroform A1 0.085 2 0.080 3 0.075 30 Good Tragacanth 0.070 . None 4 B1 0.040 15-20 Very thick Benzene 2 0.030 25 Good 0.020 gram 3 0.020 30-35 Thin Tragacanth 4 0.015 . h-one c 1 0.070 Carbon 2 0.060 25-30 Good 0.060 gram tetraTragacanth 3 0.055 . None chloride D1 0.08 None Oil 2 0.10 . None of Turpentine 3 More than 0.10 g. forms thick, unmanageable mass E1 0.07 60 Thick, but separates Almond Oil 2 0.05 . , Thick, separates in 3 mins. 3 More than 0.07 g. forms unmanageable mass
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. ...
SPECIALCASESAND REMARKS (a) 10 cc. chloroform plus 0.08 g. tragacanth and water added in 0.5 cc. portions, shaking after each addition, required a total of 10 cc. water for emulsification, and the emulsion thus formed showed a separation of 25 per cent its volume after 12 hrs. Emulsions 1 and 2 show no such separation. ( b ) 10 cc. chloroform, when shaken with a mucilage previously prepared from 0.08 g. tragacanth and 7.5 cc. water gave no emulsion: 10 cc. chloroform formed no emulsion when shaken with mucilages containing 0.10 and 0.20 g. tragacanth, respectively, in 7.5 cc. of water. (a) and ( b ) emphasize the necessity of hydrating the emulsifier all a t once and in the presence of the internal phase. (c) If chloroform is allowed to stand in contact with the tragacanth for 15 hrs. before the water is added the critical point is not changed. ( d ) The globules of the chloroform emulsions showed a motion similar to the Brownian movement: the benzene and carbon tetrachloride emulsions with tragacanth do not. B ( a ) The critical point is not influenced if the benzene is allowed t o stand in contact with the tragacanth for 15 hrs. before adding the water. C (a) If dry, distilled carbon tetrachloride is allowed to stand in contact with the tragacanth for 15 hrs. before adding the water, the critical point is unaffected. If, however, carbon tetrachloride which had previously stood in contact with water for 1 hr. and was then siphoned off and emulsified without being dried, i t gave the following discordant results: 10 cc. plus 0.4 g. tragacanth plus 7.5 cc. water gave no emulsion. 10 cc. plus 0.05 g. tragacanth plus 7.5 cc. water gave good emulsion. 10 cc. plus 0.06 g. tragacanth plus 7.5 cc. water gave no emulsion. 10 cc. plus 0.07 g. tragacanth plus 7.5 cc. water gave good emulsion. This experiment was repeated three times with the same result. D-E (a) Tragacanth takes up water rapidly, forming a spongy mass which shows little tendency to emulsify fixed oils and so is greatly inferior to acacia if they are t o be emulsified by shaking. Hiss1 has shown t h a t i t is also inferior where the method of trituration is employed.
A
1
Bull. Pharm., 13 (1899). 229.
,
