T H E J O U R N A L O F I N D U S T R I A L A N D E ;VGI N E E RI N G C H E M I S T R Y
A%., 1917 CHzCl ~
CHzCl
-
CHzOzCH
+2HCOsXa+
CHiOzCH
I
CHzOzCH
4- 2CHsOH
I
CHzOzCH CHzOH L O H
+ 2KaC1
(1)
+ 2HCOzCHz
(2)
+
By employing considerable excess methyl alcohol t h e equilibrium is maintained by proportionately more glycol formate being converted t o glycol, which amounts in t h e experiments here noted t o about 8 j per cent conversion. E X P E R I ME N T A L
The experiments tabulated below indicate t h a t t h e conditions for maximum yields are: heating t h e reaction mixture, consisting of one mol of, ethylene chloride in five volumes of methyl alcohol a n d about three mols of sodium .formate, t o a temperature of 1 6 j t o 170' C. for about 7 hrs. At this temperature t h e pressure will vary from about 2 4 0 lbs. at t h e beginning t o 290 lbs. per sq. in. after 7 hrs., and a pressure, when cold, of about j o lbs., which.latter pressure is undoubtedly due t o t h e decomposition of a small amount of sodium formate. When autoclaves of several liters capacity are employed, i t is highly desirable t o stir t h e contents, which is most simply done by slowly rotating t h e autoclave.' Above 1 7 j ' C. large proportions of diglycol are formed as is shown b y Experiments 19 a n d 2 7 . TABLE I-YIELD
GLYCOL BY ACTION OF SODIUM FORMATE A N D METHYL ALCOHOL O N ETHYLENE CHLORIDE KO.O F MOLSUSED TREATMENT PRESSURE YIELD Exp. Ethylene Sodium Methyl Temp. Time Max. Cold Per cent of ,No. Chloride Formate Alcohol Lbs. Lbs. Theoretical C. Hrs. 13.0 105 4 3 45-5 0 5 2.5 13.0 140 8 100 * 5 15 32 16 2.5 165 7 13.0 195 * 5 25 55 7 2.0 165 7 13.0 220 * 10 30 65 10 2.5 250 70 6.5 170 5 4 10 25 17 2.5 12 165 f 5 7 13.0 82 260 10 55 4.0 60 165 f 5 8 29 13.0 .... 40 4.0 60 240 * 10 40 1,O f 5 6 28 13.0 4.0 1 . 5 250 * 10 0 li5 f 5 15 6.5 21 2.5 35 5 4 10 , . 165 6.5 220 23* 2.5 13.0(c) 160 f 5 8 79 2.7 .... .. 24t 175 f 5 7 13.0 2.7 .... ,. 19t .... .. 180 f 10 10 13.0 2.7 27t * 5 grams HgSOd added. t In rotating autoclave. ( a ) 40 grams. ( b ) 300 grams. (c) 1500 cc. ( d ) 18 per cent "diglycol" also obta.ined. (e) 35 per cent "diglycol" of b. p. ;215 to 250' C. also obtained. OF
f
f
f
-
Ex?
T h e general procedure for isolating t h e glycols was as follows: After cooling, t h e slight "cold pressure" was released, t h e methyl alcohol solution poured from t h e crystalline salt and sodium formate mixture, t h e latter washed with a little cold methyl alcohol and t h e combined alcoholic solution distilled. GLYCOL F R O M ETHYLENE CHLORIDE B Y THE ACETATE METHOD TREATMENTPRESSURE GRAMSMATERIALS USED YIELD Temp. Time in Exp. Ethylene Sodium Sol-. Per cent of C. Hrs. Lbs. No.Chloride Acetate vent Theoretical 4 50 115 75(a) 170 f 5 4 150 * 10 32(c) 5 8 175 f 10 34(c) 6 50 115 75(a) 185 7 110 37(d) 8 65 65 110(b) 160 ( a ) Acetic acid. ( b ) Ethylalcohol (sp. gr. 0.83). (c) Diacetate hydrolyzed by alcoholic HCl: see Henry, Chem. Zentr., l ( 1 9 0 7 ) . 1314. ( d ) This method yields the monoacetate: cf. Erlenmeyer, Ann., 192, 244; Demole. A n n . , 173, 117.
TABLE11-YIELD
OF
f
I n some cases t h e methyl alcohol was distilled a t ordinary pressure a n d t h e glycol then distilled in vacuo. I n most cases, however, t h e glycol was distilled a t atmospheric pressure. 1 This keeps the contents well mixed, prevents the formation of a salt cake in the bottom of the apparatus and very materially improves the yield as has already been shown by us in the case of the preparation of amyl acetate from chlorpentane, anhydrous sodium acetate and acetic acid. Cf. U. S. Patent No. 1,197,019.
751
The reaction of ethylene chloride with sodium acet a t e in glacial acetic acid takes place less readily, as is indicated by t h e lower yields in Experiments 4 and 6 in Table 11. A very small fraction boiling between 170' and 180' C. was always obtained, amounting usually t o 8 t o I O per cent of t h e weight of t h e dichloride employed, which consisted of glycol diformate, boiling point 174' C.' Saponification of I O g. of this ester yielded 7 . j g. of glycol, boiling point 190-196' C. MELLON INSTITUTE O F I N D U S T R I A L RESEARCH O F PITTSBURGH, PITTSBURGH, P A . UNIVERSITY
IODOMETRIC DETERMINATION OF CHLORINE I N CHLORIDES By GREGORY TOROSSIAN
Received May 10, 1917
With t h e object in view of determining chlorine in chlorides quickly and accurately and without t h e use of silver nitrate, t h e well-known method for valuation of the available N n O s by iodine was applied. I n t h e determination of t h e available MnOz b y iodine t h e sample is treated with a quantity of hydrochloric acid in a small distilling flask, t h e liberated chlorine is carried through a glass tubing into a solution of potassium iodide and t h e liberated iodine is titrated with a N / I O sodium thiosulfate solution. I n t h e proposed method for t h e determination of chlorine in chlorides t h e sample is mixed with finely powdered manganese dioxide, a n d treated with sulfuric acid ( I : I by vol.) in a distilling apparatus, as in the MnOz determination, and t h e chlorine, produced by t h e interaction of M n 0 2 and t h e HC1 set free from t h e chloride sample by the action of HzS04, is conducted into a K I solution a n d the liberated iodine titrated as usual with N / I O Ka2S2O3. I n this reaction between sulfuric acid and a chloride in t h e presence of l l n O z , t h e chlorine from t h e chloride is all distilled off, t h e spent liquor showing no chlorine when tested with A g S 0 3 . The reaction appears t o be: 2XaC1
+ 2HzS04 + MnOz = NazSOd + MnSOA + 2Hz0 + CL. LIETHOD
I ) Finely ground MnOz (passing Ioo-mesh sieve). ( 2 ) Sulfuric acid ( I : I by vol.) free from nitric, hydrochloric acids, nitrates and nitrous fumes, etc. (3) Potassium iodide solution, 2 j grams per liter. (4) X/IOsodium thiosulfate solution.
T H E R E A G E K T S REQUIRED-(
T H E A P P A R A T U S used is the same as in t h e case of MnOz determination b y distillation with hydrochloric acid and is shown in t h e accompanying sketch
T H E S A X P L I N C in this method is very important. In t h e case of solids t h e sample must be finely powdered t o insure intimate mixing with t h e manganese dioxide. If this is not done, there may occur a loss of chlorine during t h e operation or incomplete decomposition of t h e chloride. I n t h e case of liquids the sample must be measured from a burette if percentage by volume is required or weighed in t h e flask directly without adding any water. The amount of sample to be taken 1
Grimaux. Bw., 1 (1874). 263.
752
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
for t h e analysis varies from 0 . 1 2 t o j g., depending on the amount of chlorine present. For liquids, from 0.5 t o 5 cc. or weights corresponding t o these figures, are taken. PROCEDURE-The weighed sample is thoroughly mixed on the weighing glass with about 2 g. of finely powdered manganese dioxide' and transferred into t h e
can be run and appropriate correction made. T h e highest blank consumption of N / I O Na2S2O3 did not run over 0 . 2 cc. in t h e author's experience and this was due t o nitric acid found in t h e sulfuric acid used. TABLEI-RESULTS BY SILVERCHLORIDE AND BY AUTHOR'S METHOD On Basis of 1 Cc. NazSOa = 0.0038204 G. C1 MATERIAL ANALYZED NO. Sodium Chloride (NaC1). . . . . . . 1 2
3
4
w A
Potassium Chloride (KCI) . . . . . . 1 2 3 4 5
D
6
7
APPARATUS FOR THE DETERMINATION O F CHLORINE IN CHLORIDES B Y DISTILLATION
3
round-bottomed flask A ; jo cc. of sulfuric acid (I : I by vol.) are added and a t once t h e flask is attached t o t h e glass tubing B , which is inserted into the larger glass tube C containing IOO cc. of K I solution and surrounded with cold water in the cylinder D. The flask is now slowly heated with a gas burner and constantly agitated, not too strongly, but just enough t o keep t h e contents in motion until boiling. The boiling is intermittently continued, with occasional agitation, for 3 t o 5 minutes, when all chlorine is distilled over into t h e K I solution. The boiling is stopped, t h e flask quickly removed, and the glass tubing washed, inside and outside, into the main solution, which is transferred into a 600 cc. pear-shaped flask, then brought t o a volume of about 2 0 0 cc. and titrated with a N / I O sodium thiosulfate solution previously standardized against pure iodine. One equivalent of iodine is equal t o one equivalent of chlorine: I cc. N / i o NazSzO3 = 0.003546 g. C1. When a liquid is t o be analyzed, t h e manganese dioxide is simply added t o t h e sample in t h e flask. If t h e chlorine in fluorides is t o be determined t h e procedure is carried out in the same way as for the other samples. Some H F will be evolved, but it has no effect upon t h e final results and its action upon the glass is negligible. If t h e sulfuric acid is free from nitric and hydrochloric acids, chlorides, nitrates and nitrous fumes, and t h e manganese dioxide contains no impurities capable of decomposing K I on volatilization, the boiling of t h e sulfuric acid and MnOn for over 8 or I O minutes does not produce any appreciable coloration in t h e K I solution. The sulfuric acid may be heated otherwise a blank test t o fuming t o drive off "03, 1 For
larger samples the amount of MnOz can be increased.
Vol. 9, No. 8
BaClz.2HzO.. . . . . . . . . . . . . . . . . . CuCh.2HzO.. ................. CuCIz.2KC1.2HzO.. . . . . . . . . . . . Dry Cell Mixes., . . . . . . . . . . . . . 1 2 1 Chloride Liquors (containing Mu, 2 3 Zn. NHa and Ca) Rare Earth Fluorides. ......... 2 2 Manganese Ores.. 1 2 3
60.66
... ... ..* ... ... ...
60.66
47.56
... ... ... ... ... ...
47.52
29.03 41.59 44.45
28.82
... ... .
.
..........
... ..... .
.............
... ... ...
... ... ... ... ,.. ...
...
... ... ... ... ...
... ...
5.78 5.. 4 0 17.75 13.48 10.92 0.10 0.23 ~~
... ...
...
60.74' 60.51 60 91 70:67 60.73 60.87 60.81 47.49' 47.49 47.49 Av. 47.61 47.61 47' 53 47.51 47.54 28.95 41.59 44.67 5.74 5.49 17.65 13.04 11.06 0.13 0.24 0.001 0.005 0.002
.fc75
.
I n Table I are tabulated t h e results of some determinations of chlorine in chlorides and products containing chlorides by t h e above method. If values in Table I for sodium chloride, which, by precipitation, gave 6 0 . 6 6 per cent C1 (the theoretical content), are used for the standardization of t h e sodium thiosulfate solution, the mean value for I cc. NazSz03 gives 0.003815 g. C1, and if this value is used t o calculate C1 in t h e potassium chloride (Table I ) t h e following figures are obtained: Potassium Chloride No.: 1 2 3 4 5 6 7 Av. Percent Chlorine.. . 47.42 47.41 47.41 47.53 47.54 4 7 . 4 4 47.41 4 7 . 4 6
The figures given in this paper were obtained under the ordinary technical analytical laboratory conditions and no claims of extreme precautions and care are made by the author, but from t h e results given it is clear t h a t t h e errors in t h e determination of chlorine in chlorides by t h e iodometric method described above are negligible for most purposes of ordinary laboratory analysis. The sodium thiosulfate solution can be standardized against sodium chloride which previously has been standardized by precipitation with AgNOa, and the mean of t h e three determinations taken a s expressing t h e strength of the Na2S303solution, but the standardization against pure resublimed iodine answers t h e purpose very satisfactorily. This method of iodometric determination of chlorine in chlorides is a very simple operation, inexpensive a n d accurate, and exceedingly quick; t h e entire procedure from weighing of t h e sample t o t h e titration of t h e iodine does not consume more t h a n I j minutes. By this same method HC1 in a mixture of hydrochloric and sulfuric acids can easily be determined without any precipitation. This method also will serve as a quick qualitative test for ascertaining whether a given sample contains chlorine and t h e possible amount. NATIONAL CARBONCOMPANY, INC. OHIO CLEVELAND,
