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Fry and Porritt, Trans. Inst. Rubber Ind.. 3, 203 (1927). Garner, Ibid., 4, 413 (1929). Grenquist, I N D . E N Q . CHEM., 21,665 (1929); 22, 759 (1930). Hauser, Kautschuk, 5, 151 (1929). ESG.CHEK 20,300 (1928). Haushalter, Jones. and Schade, IND. Karrer, Davies, and Dieterich, Ibid., Anal. E d . , 2, 96 (1930). Krenan, Chem. Rev., 3, 95 (1926). Messenger, Trans.Inst. Rubher Ind., 5,71 (1929). Park, Carson, and Sebrell, IND. E N G . CHEM., 20,478 (1928). Pohle, Kolloidchem. Beihefte, 13, 1 (1920). Pummerer. Nielsen, and Gundel, Ber., 60,2167 (1927). Russell, Proc. Roy. SOC.(London),61,424 (1897). (19) Saeland, Ann. Physik, 26,899 (1908). (20) Shacklook, Trans. Inst. Rubber I d . , 6,259 (1930). (21) Sheppard and Wightman, J. Franklin Inst., 195,337 (1923). (22) Staudinger, Swiss Patent 119,027 (1927)
(7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18)
CHEMISTRY
Vol. 24, No, 2
(23) Staudinger, Ann., 468, 1 (1929); Gummi-Ztg., 43, 1928 (1929); Kolloid-Z.. 51, 71 (1930). (24) Stutz, Nelson, and Schmuts, IND.ENG.CHEM.,17, 1138 (1925). (25) Taffel and Revis, J. SOC.Chem. Ind., 50,87T (1931). (26) Tomlinson, Proc. Roy. SOC.(London),A115,472 (1927). (27) Van Rossem, Trans. Inst. Rubber I d . , 1, 73 (1925). ENG.CHEM.,18, 1152 (1926). (28) Van Rossem and Dekker, IND. (29) W&gand, Rubber Age (Ar. Y . ) , 28, 615 (1931). (30) mightman, Trivelli, and Sheppard, J. Franklin Inst., 200, 335 (1925). (31) Worthington and Hyde, U. S. Patent 1,360,486 (1920). RECEIVED September 10, 1931. Presented before the Divieion of Rubber Chemistry at the 82nd Meeting of the American Chemioal Society. Buffalo, N Y., August 31 to September 4, 1931.
Stability of Chlorohydrocarbons I. Methylene Chloride P. J. CARLISLE AND A. A. LEVINE,The Roessler Q Hasslacher Chemical Co., Inc., Niagara Falls, N . Y.
M
ETHYLEKE chloride, a low-boiling chlorohydrocarbon, has found extensive use as a refrigerant in air conditioning, and as a solvent for cellulose acetate, as a general low-boiling solvent, and as an intermediate in organic synthesis. It does not form explosive mixtures with air, and on this account may be useful where a safe low-boiling Yolvent is required. The present paper discusses the stability of methylene chloride alone or in contact with various substances and over a wide range of temperatures, and the possibility of corrosion of the common metals by methylene chloride. The physical properties of methylene chloride are as follows: Formula Molecular weight
Color
Odor
Sp. gr. (20°(4' C.) Freezing point C. Boiling point (760 mm.), O C. Surface tension against air (18" C.), dynes/cm Refractive index Coefficient of viscosity (20.53' C.) Solubility in 100 grama HsO (20' C J , gram8 Specific heat Latent beat of vaporization, cal./gram (B. t. Ib.) Critical temperature, C.
CHtClr 84.92 Wat er-white Sweet. uleasant. similar to chlbroform 1.3361 -96.7 39.8 26.52
1.4234 0.004414 2,000 0.287
75.3 (135.8) 245.1
EXPERIMENTAL PROCEDURE Glass tubes, 2.5 by 25 cm., were prepared and provided with a 5-mm. constriction to facilitate sealing. Each of these tubes received 25 cc. of methylene chloride, distilled in an atmosphere of nitrogen prior to the experiment; and, where specified, water, oxygen, and metal strips were also added (as shown in Tables I and 111). A series of these glass tubes was placed inside capped iron pipes; and these were then immersed in electrically heated oil baths, maintained a t 40", 60", 80", loo", 120°, and 140" C., * 2", for 24 hours. After cooling, the tubes were opened and the contents transferred to a titration flask, 25 cc. of neutral distilled water added, and any developed acidity titrated with 0.01 N alkali, using phenolphthalein as indicator. The results are given in Table I. The metal strips were cleaned, polished, rinsed with methylene chloride, and weighed. After removal from the glass tubes, the strips were wiped clean and weighed. The loss in weight per square centimeter of surface is tabulated in Table 11.
The methylene chloride used throughout this investigation was a commercial grade conforming to the following specifications: Acidity Boiling range (760 mm ), Residue on evaporation Moisture Color Odor
' C.
None 39.5-39.8 Faint trace None Water-white Normal
DISCCSSION OF RESULTS In this study it was assumed that the decomposition of methylene chloride is proportional to the amount of free acid formed. This is not strictly true, since decomposition may occur without forming free acids; furthermore, if free acids are formed, they may combine with polymerized decomposition products to give neutral substances. For the purpose of the present investigation, however, the acidity developed gives data of real value. EFFECTOF TEMPERATURE ON DECOMPOSITION OF METHYLENE CHLORIDE.No decomposition occurred below 120" C. when methylene chloride was heated for 24 hours in sealed tubes. At 120" C., 1.2 cc. of 0.01 N hydrochlorit acid for 25 cc. was found, indicating that methylene chloride is stable at these temperatures. At 200" C. an acidity of 0.0002 per cent by weight of hydrochloric acid developed when the vapor of methylene chloride was passed through an iron tube with a contact time of 1 to 3 seconds. This decomposition is negligible. At 300" and 400" C. the acidity amounted t o only 0.0032 and 0.0115 per cent by weight. At 500" C., marked decomposition occurred. The acidity a t this temperature amounted to 0.044 per cent by weight of hydrochloric acid. EFFECTOF WATERON DECOMPOSITION OF METHYLENE CHLORIDE.Hydrolysis of methylene chloride would be expected to result in the formation of hydrochloric acid and formaldehyde; therefore, wherever moisture was present in a determination, Schiff's test for formaldehyde was applied. The amount of water present has a decided influence on the decomposition of methylene chloride. With just enough water to saturate it a t room temperature, decomposition was observed a t 100" C. At 120" and 140" C. this decomposition was slightly greater. No formaldehyde was found when using Schiff's reagent. With an excess of water (1 mole of methylene chloride to 2 moles of water) hydrolysis started a t 60" C., about 20" above the boiling point of the solvent;
February, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
147
this increased rapidly with temperature, so that a t 140" C. steel, the acidity was 41.2 cc. of 0.01 W hydrochloric acid 2281 cc. of 0.01 LV hydrochloric acid had formed, indicating at the same temperature. X o decomposition was observed that about 3.4 per cent of the methylene chloride mas hy- when the solvent was refluxed with 1.5 per cent of water and drolyzed in 24 hours. Positive test for formaldehyde in- soft steel for 8 days. Decomposition occurred only a t dicated its presence. KO hydrolysis occurred at the boiling temperatures above the boiling point of this solvent. temperature. Rlethylene chloride was refluxed for 8 days in 111. CORROSIVE EFFECT OF METHYLEVE CHLORIDE OY the presence of 1.5 per cent water, with no development of TABLE VARIOUS hfET.4LS acidity. (In milligrams per square centimeter) EFFECTOF OXYGENON DECOMPOSITION OF METHYLENE EXPERIMEKTAL CHANGE I N WEIGHT O N HEATING 24 HOURS CHLORIDE.Pure oxygen or oxygen in the air had no apCONDITIONS AT: 60OC. 80" C. 1 0 0 ° C . 120" C. 140' C . parent effect on methylene chloride below 140" C. This is Methylene chloride and: striking when it is recalled that chloroform is readily decom-0 03 0 0 0 ... Soft steel in nitrogen Soft steel'satd. with water, posed by atmospheric oxygen. in nitrogen 0 0 0 +0.05 +O. 05
EFFECT OF METALSON DECOMPOSITIOS OF METHYLEKE CHLORIDE.Dry methylene chloride, or methylene chloride saturated with water, was not decomposed by soft steel on heating to 120"C. in sealed tubes for 24 hours. Methylene chloride was not decomposed on refluxing with steel in the presence of about 1.5 per cent water for 8 days. No decomposition was observed when methylene chloride was heated for 24 hours in an atmosphere of oxygen or air up to 120" C. in the presence of soft steel. TABLEI . DECOVPOSITIOV OF METHYLENE V ~ R I O U SCOWITIOYS
CHLORIDE UYDEH
(In cc of 0 01 A' HCI per 25 cc CHzClP)
EXPEFUXENTAL CONDITIONS
DECOMPOSITIOK O Y HEATING 24 H O L MAT 8OoC 1 0 0 ° C 12(I°C 140'C
40°C 6 0 ° C
Methvlene chloride dtrogen :
in
%h soft steel Satd. with water With soft steel, satd. with water With copper, aatd. with water With aluminum, satd. with water With lead. satd. with water With tin. satd. with water With brass, satd. with wvater
., ...
0 0
0
0
6.55
0
0
0.40
0
0
0
0
1.40
0.40
..
0.45
0
0.6
0.70
0.45
0
0
0.4
0
0
n
: i. 55
n 3.55
n
3.55
41.15
0 0 0 0 1.30 0
.
WitL'iicess of water . With soft steel and excess of water .. Methylene chloride and soft steel in air Methvlene chloride with 1.5% water, refluxed with soft steel for 24 hours hlethylene chloride with 1.5% water, refluxed with soft steel for 8 days: Soft steel in oxygen .. Soft steel, satd. with water in oxygen . a 1 cc. of 0.1 N HCI er 25 cc. 0.001% by weight of H81.
0
0.15
1.20 0
l2i;::
1.45 4 5 . 4 0 287.0 196.0
272.0
O.?O
0.45
,
" '
0.35
2.45 291.0 2281.0 ,..
22.00
Soft steel, excess water, in -0.67 - 3 . 1 -1.4 nitrogen -0.1 0 0 0 Soft steel, in air 0 0 0 0 Soft steel, in oxygen 0 Soft steel satd. with water, -0.1 -0.4 -1.57 -3.0 in oxygen Sbft steel 1.5% water, re(Very slight) fluxed 48 hours Soft steel 1.5% water, re(Very slight) flured d days Copper satd. with water, 0 0 0 0 in nitrogen Aluminum satd. with 0 0 0 0 water in nitrogen Lead s&d. with water, in 0 -0.2 0 -0.1 nitrogen Brass satd. with water, in 0 0.10b Ob Ob nitrogen Tin, satd. with water, in 0 0 0 0 nitrogen b Copper-colored surface. 0 Heavy coat of iron oxide.
0.013 0 0
0 0 0
1.5b 2
CORROSIVEEFFECTOF METHYLENE CHLORIDE.Aluminum, copper, tin, lead, and soft steel were not corroded by dry methylene chloride or methylene chloride saturated with water up to 140" C. The loss in weight of these metals was well within the experimental error for each determination. Brass was attacked a t 60" C., changing the surface to bright copper-like color, indicating that the zinc was dissolved. Soft steel was not corroded with methylene chloride on refluxing with an excess of water for 8 days. At higher temperatures the solvent with an excess of water corroded soft steel owing to hydrolysis. Methylene chloride is the least corrosive of the higher chlorinated hydrocarbons. Its corrosive effect is hardly greater than that of water. SUM%l.kRY
1. Methylene chloride has been found to be stable up to 120" C., about 80" above its boiling point. 2. Small quantities of water do not appreciably affect the (Acidity-0.05 cc.) stability of methylene chloride a t temperatures below 100" C. 0.15 0.10 0.75 0 0.25 3. The presence of an excess of water causes no decom0 0.10 80.7 80.90 ... position of methylene chloride at its boiling point; a t higher of solvent is equivalent approximately to temperatures, some decompositions take place. 4. Soft steel, copper, aluminum, lead, and tin have no TABLE11. VAPOR-PHASE DECOMPOSITION OF METHYLENE effects on the decomposition of methylene chloride. Brass, up CHLORIDE to 80" C., has a negligible effect. 400 500 200 300 Temperature, C. 5. The combined influence of water and soft steel, copper, 10.86 40.11 0.05 2.99 0 . 0 1 N alkali, cc. 0.0032 0.0115 0.044 HCI by weight, % 0.0002 aluminum, lead, brass, and tin does not affect decomposition of methylene chloride a t temperatures up to 100" C. Copper, aluminum, brass, tin. and lead had no effect on the 6. Pure oxygen or oxygen from the air has only a slight decomposition up to 140" C. Methylene chloride was not effect on the decomposition of methylene chloride up to affected by these metals to any marked extent. 120" c. COMBINED INFLUENCE OF WATERAND METALS ON DECON7 . The combined effect of oxygen and soft steel on the POSITION OF METHYLENE CHLORIDE.The influence of each decomposition of methylene chloride is negligible even a t of these factors has already been noted. The combined 140" C. influence of both water and metals on the decomposition 8. The combined effect of soft steel, oxygen, and moisture of methylene chloride is negligible up t o 120" C. if just enough on the decomposition of methylene chloride is negligible up to water is present t o saturate the methylene chloride. In 80" C. the presence of an excess of water and soft steel, the decom9. Various metals, such as soft steel, aluminum, copper, position of methylene chloride is more extensive than if mater tin, and lead, are not corroded by methylene chloride satualone is present in excess. For instance, a t 80" C. the acidity rated with water. Brass is attacked above 60" C. was 3.5 cc. of 0.01 A' hydrochloric acid per 25 cc. when water alone was present in excess. JJ'ith excess water and soft RECEIVED September 30, 1931 (Acidity-none)
