US3609091A

US3609091A - Stabilized solvent

Info

Publication number: US3609091A
Application number: US878541A
Authority: US
Inventors: Eleanor Harden; Robert Stewart Gow
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1969-11-20
Filing date: 1969-11-20
Publication date: 1971-09-28
Anticipated expiration: 1988-09-28

Abstract

There is provided a composition of 1,1,1-trichloroethane which has as stabilizer therefor an alkyl or alkoxyalkyl ester of nitric acid which contains less than 5 carbon atoms per molecule and mixtures thereof. The stabilizer may be in the amount of 0.5 to 10 percent by weight of the 1,1,1-trichloroethane. Additional stabilizers may be included in the composition, among which are acrylonitrile and butene oxides.

Description

United States Patent [50] Field of Search 252/171, 172,153,401, 405, 364; 106/311;260/652.5

[56] References Cited UNITED STATES PATENTS 2,436,772 2/1948 Klabunde 252/ I 71 3,060,125 10/1962 Sims 252/171 3,265,747 8/1966 Cormany et al. 252/ 1 71 Primary Examiner-Leon D, Rosdol Assistant Examiner-William E. Schulz Attorney-Cushman, Darby and Cushman ABSTRACT: There is provided a composition of 1,1,1- trichloroethane which has as stabilizer therefor an alkyl or alkoxyalkyl ester of nitric acid which contains less than 5 carbon atoms per molecule and mixtures thereof. The stabilizer may be in the amount of 0.5 to 10 percent by weight of the 1,1,1- trichloroethane. Additional stabilizers may be included in the cbmposition, among which are acrylonitrile and butene oxides.

STABllLllZElD SOLVENT This is a continuation-in-part of US. application Ser. No. 459,880, filed on May 28, 1965, which application was continued as application Ser. No. 852,522, now abandoned.

Chlorinated hydrocarbons are widely used as solvents for metal degreasing operations, and a variety of stabilizers have been proposed for use in preventing decomposition of the solvent and corrosion of metals in contact with the solvent. 1,1,1- trichloroethane is very efiective and safe for many applications, for example for the removal of grease from metals in the cold, but has a greater tendency to decompose in the presence of aluminum under such conditions than the commoner solvents such as trichloroethylene and tetrachloroethylene.

Consequently, many of the materials which function quite adequately as stabilizers in other solvents provide at best only short term stabilization of the 1,1,l-trichloroethane. Some metals, particularly some aluminum alloys, are more readily attacked than others, and it is very desirable that the solvent should be sufficiently stabilized to withstand prolonged contact with these very active metals or alloys even though, in use, such active metals may make up only a small proportion of the metal normally expected to be in contact with the solvent.

We have now found that efficient stabilization of the 1,1,1- trichloroethane against metal-induced decomposition can be achieved by addition of an organic nitrate. By an organic nitrate we mean an organic ester of nitric acid.

The organic nitrate may be for example an aromatic nitrate but we prefer to use aliphatic nitrates. Certain aliphatic nitrates, particularly those containing more than one nitrate group, tend to be explosive and great care should be exercised in the use of such compounds. We have found that aliphatic mononitrates, namely the alkyl esters and alkoxyalkyl esters of nitric acid containing less than 5 carbon atoms per molecule, are most suitable. In particular we prefer to use isopropyl nitrate as it is easily accessible and has a suitable boiling point. Mixtures of the said esters of nitric acid may also be used if desired. The efficiency of these esters varies so that the optimum proportions are not necessarily the same for all the compounds in the group.

In general, proportions of the esters of nitric acid in the range 0.5 to percent and preferably 1 to 4 percent by weight of the l,l,ltrichloroethane are suitable.

Thus according to the invention we provide a 1,1,1- trichloroethane composition containing a member of the group consisting of alkyl esters and alkoxyalkyl esters of nitric acid which contain less than 5 carbon atoms per molecule and mixtures of the said esters as stabilizer for the 1,1,1- trichloroethane in amount of 0.5-l0 percent preferably l-4 percent by weight of the l ,l,1-trichloroethane.

When solvents are used cold, as is often the case with 1,1,]- trichloroethane, the accumulation of grease and dirt in the solvent during the degreasing process makes it economically desirable that the dirty solvent should be redistilled to recover valuable clean solvent. Furthermore, it is sometimes the practice to use l,l,l-trichloroethane in metal degreasing processes in which the workpieces are treated in the boiling solvent or its vapor, and it will be understood that in both degreasing using hot solvent, and in distillation, solvent vapor is continuously being liberated from a bulk of boiling liquid and must consequently be condensed back to the liquid state. For a stabilizer to be suitable in industrial practice, therefore, it should not only be capable of performing its chemical stabilizing function but should also be such that it is not appreciably separated from the l,l,l-trichloroethane during distillation. For this reason we prefer to use alkyl esters and alkoxyalkyl esters of nitric acid whose boiling points at normal atmospheric pressure do not exceed 130 C. although higher boiling members of this group of compounds also have some stabilizing action.

We prefer to include in the composition, in addition to the ester of nitric acid, one or more members of one or more of the following groups of compounds, i.e. nitriles,-ethers, alcohols, ketones, nitroalkanes, carboxylic esters and morpholines. We particularly prefer to use one or more of the following compounds, i.e. acetonitrile, acrylonitrile, propionitrile, dimethoxyethane, isobutanol, tertiary butanol, tertiary amyl alcohol, ethyl acetate, isopropyl acetate, ethyl methyl ketone, nitromethane and nitroethane. Especially we prefer to use a composition containing one of the following groups of components.

1. An alkyl ester of nitric acid and a nitrile.

2. An alkyl ester of nitric acid and a tertiary alcohol.

3. An alkyl ester of nitric acid and a carboxylic ester.

4. An alkyl ester of nitric acid and an ether.

5. An alkyl ester of nitric acid and a nitroalkane.

6. An alkyl ester of nitric acid, a nitrile and a nitroalkane.

7. An alkyl ester of nitric acid, a nitrile and a tertiary alcohol.

8. An alkyl ester of nitric acid, a tertiary alcohol and a nitroalkane.

All the compounds mentioned are generally soluble in chlorinated hydrocarbon solvents, and, as they generally do not react with the oil, grease and fatty compounds present on the surface of the articles which are commonly degreased in such solvents, are therefore suitable for continual use as stabilizers in l,l,l-trichloroethane. We prefer to use stabilizers, other than the nitrate, whose boiling point is below C. to avoid separation of the stabilizers from the 1,1,1- trichloroethane during distillation; however stabilizers of higher boiling point may also be used.

As will be seen from the examples the addition of other stabilizers to a composition containing an alkyl ester or an alkoxyester of nitric acid may produce a solvent whose stability is considerably greater than could be expected from the stabilities produced by the two stabilizers when used separately.

We have found that proportions of nitrile, ether, alcohol, ketone, nitroalkane, carboxylic ester, or morpholine, in the range 0.5 to 10 percent and preferably in the range 0.5 to 4 percent by weight of the l,l,l-trichloroethane are suitable in combination with an organic nitrate. We also prefer to use a composition in which the combined stabilizers represent not less than 3 percent (for most purposes not less than 4.5 percent) and not more than 10 percent by weight of the 1,1,1- trichloroethane.

For effective stabilization the quantity of the ester of nitric acid and of the other component(s) to be used may be found to vary somewhat according to the particular stabilizers employed and the particular conditions of use, for example, the particular metals to be in contact with the solvent. Smaller amounts than those indicated may provide a useful stabilizing effect, but in commercial practice it is advisable to keep the proportions above the minimum value given in order to provide an adequate margin of safety. Proportions greater than those in the ranges given may be used ifdesired, but little additional stabilization is thereby achieved.

It must be understood that the stabilizers of the present invention may furthermore be used in conjunction with other conventional stabilizing systems. For example it is known that decomposition of chlorinated hydrocarbons can occur by hydrolysis under the influence of heat and water and in the presence of metals such as iron or zinc with the development of acidity, and it has been proposed to inhibit this type of decomposition or to remove the acidity as it is formed by the use of various additives, for instance neutral acid-acceptors such as epoxides. We have found that proportions of epoxide in the range 0.l to 1.0 percent by weight of the 1,1,1- trichloroethane may be used satisfactorily in combination with the above-mentioned compositions. Suitable epoxides are the aliphatic epoxides containing 3-6 carbon atoms per molecule, particularly the isomeric butene oxides, mixtures of these isomers as readily available commercially and epichlorohydrin.

A particularly useful composition is one which consists of 1,1, l-trichloroethane containing about 2 percent by weight of isopropyl nitrate, about 2 percent by weight of acetonitrile, 0.75-1 percent by weight of nitromethane and about 0.25 percent by weight of a butene oxide. Compositions of similar high performance under most conditions of use can, however, also be devised without the use of the relatively expensive nitromethane by employing acrylonitrile as the nitrile component. In accordance with this feature of the invention we incorporate in the l,l,l-trichloroethane as stabilizers therefor 2-4 percent of any alkyl ester or an alkoxyalkyl ester of nitric acid containing less than carbon atoms per molecule, 0.5-4 percent of acrylonitrile and 0. l-l percent of butene oxides, all calculated on the weight of the l, l, l-trichloroethane. A preferred combination of stabilizers within these limits comprises about 3 percent isopropyl nitrate, about 2 percent acrylonitrile and about 0.25 percent butene oxides.

To achieve even greater long-term stability or to increase the margin of protection against metal-induced decomposition of the solvent when the amount of acrylonitrile is kept near the lower end of the stated range, a proportion of a nitroalkane, e.g. 0.5-2 percent of nitromethane or nitroethane may still be added to the aforesaid compositions containing acrylonitrile if desired. Optionally also one or more of the other chemical types of auxiliary stabilizers mentioned hereinbefore may be added to these compositions containing acrylonitrile, especially one or more of dimethoxyethane, isobutanol, tertiary amyl alcohol, isopropyl acetate and ethyl methyl ketone. The most suitable proportion for each of these auxiliary stabilizers is 0.5-4 percent of the weight of the 1,1,1- trichloroethane. 0.5

Compositions according to our invention may be used as a solvent particularly in conventional degreasing and cleaning processes and apparatus and may be put to all the other conventional uses of l,l,ltrichloroethane in which the presence of the stabilizers is not objectionable,

The invention is illustrated but not limited by the following examples in which the parts and percentages are by weight.

EXAMPLE 1 30 ml. of the composition under test were refluxed at a temperature of about 74 C. with 4 grams of an active aluminum alloy (specification 2 to 4 percent of copper, 3 to 6 percent of silicon, less than 0.8 percent of iron, less than 0.7 percent of manganese, less than 0.2 percent of magnesium, zinc and nickel, remainder aluminum) with the following results.

a. Unstabilized l,l,l-trichloroethane reacted immediately with evolution of hydrochloric acid and formation of dark tarry products.

b. A solution of 3 percent of isopropyl nitrate in l, l, 1-

trichloroethane showed no sign of reaction when it had been refluxed for 500 hours.

EXAMPLE 2 We have found that the following test is extremely rigorous and enables us to test the effect of stabilizers in a relatively short time.

A brass screw threaded into a block of Duralumin (an alloy consisting of9 l .5 percent of aluminum, 4 percent of copper, 1 percent of magnesium, 1 percent of iron, 1.5 percent of silicon, 1.2 percent of manganese and 0.25 percent of nickel), was ultrasonically irradiated at a frequency of 40 kHz. per sec. while immersed in the composition under the test. The temperature of the composition was maintained at 30 C. throughout the test. Every 5 minutes throughout the test the screw was unscrewed and the thread in the Duralumin block was inspected for corrosion and for the presence of tarry products. When unstabilized l,l,l-trichloroethane is submitted to this test tar formation occurs almost immediately. The results are shown in Table 1.

Table 1 -Continued 5 lsopropyl Nitrate 60 mins. 3 Dimethoxyethane 10 mins. 3 Tertiarybutyl Alcohol l0 mins. 2 Acetonitrile 5 mins. 3 lsopropyl Nitrate No reaction after 2 Dimethoxyethane minutes 3 lsopropyl Nitrate No reaction after -H-2 Acetonitrile 90 minutes 3 lsopropyl Nitrate No reaction after 2 Tertiarybutyl Alcohol 90 minutes 3 lsopropyTNit rate No reaction after 2 Ethyl Acetate 90 minutes EXAMPLE 3 The test was carried out in the same way as described in example 2. The results are shown in table 2.

EXAMPLE 4 A brass screw threaded into a block of Duralumin was ultrasonically irradiated at a frequency of 40 kHz. per sec. while immersed in the composition under test. The temperature of the composition was maintained at 60 C. throughout the test. Every 5 minutes throughout the test the screw was unscrewed and the thread in the Duralumin block was inspected for corrosion and for the presence of tarry products. The results are shown in table 3.

TABLE 3 Percent of Time to Corrosion Stabilizer Stabilizer and Production of Tar 3 lsopropyl Nitrate 10 mins. l Nitromethane 3 lsopropyl Nitrate 10 mins. 2 Tcrtiarybutyl Alcohol 3 lsopropyl Nitrate 1 hr. (solvent 2 Acetonitrile yellow after 2 hr.) 3 lsopropyl Nitrate No reaction after 2 Acetonilrile 1 hour l Nitromethane 1.5 lsopropyl Nitrate No reaction after |.5 Acetonitrile l hour l.5 Nitromethane 2 lsopropyl Nitrate No reaction after 2 Acetonitrile 1 hour l Nitromcthane 2 lsopropyl Nitrate No reaction after 3 Acetonitrile 1 hour 0.5 Nitromethanc l lsopropyl Nitrate No reaction after 3 Acetonitrilc l hour (but l Tcrtiaryamyl Alcohol liquid turbid) 2 lsopropyl Nitrate No reaction after 2 Tertiarybutyl Alcohol 1 hour (but liquid l Nitromethane slightly discolored EXAMPLE 5 The test was carried out in the same way as in example 4. The results are shown in table 4.

TABLE 4 Percent of Stabilizer Time to Corrosion Stabilizer and Production of Tar 50 mins.

1 hr. no reaction 25 mins.

1 hr. slight reaction and discoloration of solvent 30 mins.

1 hr. slight reaction and discoloration of solvent 5 mins.

EXAMPLES 6-14 For each example the following test of stability was carried out to simulate the severe conditions which can occur in a liquor-vapor degreasing plant.

250 m/. of l,l,l-trichloroethane containing stabilizers as shown in the following table 5 were placed in a 500-ml. conical flask together with g. of iron filings, l g. of aluminum swarf and three strips each 3" 0.5" of copper, mild steel and aluminum and alloy respectively. The flask was surmounted by a soxhlet extractor modified so as to retain a constant head of liquid above the flask and carrying above it a reflux condenser. 50 ml. of the same stabilized 1,1,l-tricholoroethane were placed in the extractor together with strips of copper, mild steel and aluminum alloy as in the flask, the strips being arranged so as to lie partly in the liquid solvent and partly in the vapor space. The flask was heated so that the solvent boiled continuously and condensate from the reflux condenser returned continuously to the flask by way of the soxhlet extractor, overflowing from the pool of liquid therein.

When unstabilized l,l,l-trichloroethane is submitted to this test it reacts almost immediately both in the flask and in the extractor and forms tarry products. The results with various stabilizer combinations present are shown in table 5, wherein is recorded the duration of each test, the amount of acidity and chloride ion produced in the solvent and the appearance of the solvent and the metal strips at the end ofthe test.

Example 7 shows the excellent performance in this test of the three-component stabilizer system in which the auxiliary stabilizer against metal-induced decomposition is acrylonitrile at the preferred concentration of 2 percent. Examples 8-14 show results in short term tests for the same combination when the acrylonitrile is reduced to 1 percent or 0.5 percent, both with and without the addition of other auxiliary stabilizers. ln examples l3 and 14 the amount of the main stabilizer, isopropyl nitrate was also reduced.

EXAMPLE l5 The ultrasonic irradiation test of example 2 (at 30 C.) and example 4 (at 60 C.) was repeated on the stabilized compositions of examples 6 and 7. l,l,l-trichloroethane stabilized by the addition of 3 percent isopropyl nitrate, 2 percent acrylonitrile and 0.25 percent butene performed excellently at 30 C., negligible reaction being apparent. but some reaction occurred after 15 minutes at 60 C. In comparison, -l,l,ltrichloroethane stabilized by the addition of 2 percent isopropyl nitrate, 2 percent acetonitrile, 0.75 percent nitromethane and 0.25 percent butene oxide showed negligible tar formation at both 30 C. and 60 C. This demonstrates the advantage of including a proportion of the nitroalkane in the composition when the stabilized solvent is to be used under the very severe conditions of ultrasonic degreasing at high temperature.

EXAMPLES 16-18 250 ml. of l,l,l-trichloroethane containing stabilizers as shown in the following table 6 were placed in a conical flask together with 1 ml. of water and strips of copper, aluminum and mild steel. The liquid in the flask was boiled for 2 days under a reflux condenser and was then tested for its residual ability to neutralize acid (the acid acceptance value) and for the amount of chloride ion formed. The appearance of the metal strips was also recorded. The results are shown in table 6. The acid acceptance value is calculated by stirring the solvent vigorously with a measured and excess amount of hydrochloric acid and then back-titrating to neutrality. The acid acceptance value is then expressed as equivalent alkalinity of the solvent calculated as percent NaOH in weight. The acid acceptance value before the test was 0.l0for all examples.

TABLE 6 Acid accept- Chloride Example ance Appearance of ion No. Stabillsers value metal strips. produced 16 2% isopropyl nitrate. 008 Three metals Not de- 2% acetonitrile. slightly tectable. 0.75% nitromethane. spotted. 0.25% butane oxide.

17 3% isopropyl nitrate. 0.08 do D0.

2% acrylonitrile. 0.25% butene oxide.

18 3% isopropyl nitrate. 0.07 Dulled and Do. 1% acrylonitrile. spotted. 1% ethyl methyl ketone. 0.25% butene oxide.

EXAMPLES l9 and 20 An aluminum sheet was immersed in cold l,1,l-

TABLE 7 Example No. Stabilizers Result 3% isopropyl nitrate l9 2% acrylonitrile 0.25% butene oxide No decomposition after 24 hours 2% isopropyl nitrate 2% acetonitrile 20 0.75% nitromethane 0.25% butcne oxide No decomposition after 24 hours what we claim is:

1. A l,l,l-trichloroethane composition consisting essentially of l,l,l-trichloroethane and a member of the group consisting of alkyl esters and alkoxy-alkyl esters of nitric acid which contain less than 5 carbon atoms per molecule and mixtures of the said esters as stabilizer for the 1,1,1- trichloroethane in amount of 0.5-l0 percent by weight of the l, l l -trichloroethane.

2. A composition as claimed in claim 1 wherein the ester has a boiling point at normal atmospheric pressure which does not exceed C.

3. A composition as claimed in claim 1 wherein the ester is isopropyl nitrate.

4. A composition as claimed in claim 1 wherein the ester is selected from the group consisting of methyl nitrate, ethyl nitrate and 2-ethoxyethyl nitrate.

5. A composition as claimed in claim 1 wherein the amount of said esters is l to 4 percent by weight of the 1,1,1- trichloroethane.

6. A composition as claimed in claim 1 wherein said composition additionally contains from about 0.5 to percent of the weight of the l,l,l-trichloroethane of one or more members selected from the group consisting of acetonitrile, acrylonitrile, propionitrile, dimethoxyethane, isobutanol, tertiary butanol, tertiary amyl alcohol, ethyl acetate, isopropyl acetate, ethyl methyl ketone, nitromethane and nitroethane.

7. A composition as claimed in claim 6 wherein the proportion of the said members is within the range of 0.5 to 4 percent by weight of the 1,1 l-trichloroethane.

8. A composition as claimed in claim 6 wherein the combined components other than l,l,l-trichloroethane represent 'more than 4.5 percent and less than l0 percent by weight of the l, l l -trichloroethane.

9. A composition as claimed in claim 1 wherein the composition contains 0.1 to 2 percent of the weight of the l,l,ltrichloroethane of aliphatic epoxides containing 3-6 carbon atoms per molecule.

10. A composition as claimed in claim 1 wherein the composition contains 0.1 to 1 percent of the weight of the l,l,ltrichloroethane of one of the isomeric butene oxides or a mixture of the said isomers.

11. A composition as claimed in claim 1 wherein the amount of said esters of nitric acid is 2 to 4 percent by weight of the l,l,l-trichloroethane and which contains additionally 0.5 to 4 percent of acrylonitrile and 0.1 to 1 percent of butene oxides calculated on the weight of the 1,1 l -trichloroethane.

12. A composition as claimed in claim 11 which contains additionally 0.5 to 2 percent by weight of the 1,1,1-

trichloroethane of nitromethane or nitroethane. 13. A composition claimed in claim 11 which contains additionally 0.5 to 4 percent by weight of the 1,1,1- trichloroethane of one or more members selected from the group consisting of dimethoxyethane, isobutanol, tertiary amyl alcohol, isopropyl acetate and ethyl methyl ketorte 14. A stabilized solvent composition which comprises 1,] ,ltrichloroethane, about 3 percent of its weight of isopropyl nitrate, about 2 percent of its weight of acrylonitrile and about 0.25 percent of its weight of butene oxides.

15. A l,l,l-trichloroethane composition consisting essentially of l,l,l-trichloroethane and from 0.5 to 10 percent by weight of the 1,1,l-trichloroethane of an alkyl ester of nitric acid which contains less than 5 carbon atoms per molecule and from 0.5 to 10 percent by weight of the 1,1,1- trichloroethane of one or more members of the group consisting of acetonitrile, dimethoxyethane, tertiary butanol, ethyl acetate, nitromethane and nitroethane.

16. A composition as claimed in claim 15 wherein the proportion of the said members is within the range 0.5 to 4 percent by weight of the 1,1, l -trichloroethane.

17 A l,l,l-trichloroethane composition consisting essentially of l,l,l-trichloroethane and from 0.5 to 10 percent by weight of the l,l,l-trichloroethane of an alkyl ester of nitric acid which contains less than 5 carbon atoms per molecule and 0.1 to 1 percent by weight of the l,l,l-trichloroethane of butene oxide as stabilizers for the 1,1 l -trichloroethane.

18. A composition which consisting essentially of 1,1,1- trichloroethane, about 2 percent by weight of isopropyl nitrate. about 2 percent by weight of acetonitrile, about 1 percent by weight of nitromethane and about 0.25 percent by weight of butene oxide.

19. A composition as claimed in claim 6 wherein the composition contains 0.l to 1 percent of the weight of the 1,1,1- trichloroethane of aliphatic epoxides containing 3-6 carbon atoms per molecule.

20. A composition as claimed in claim 19 wherein the composition contains about 2 percent by weight of isopropyl nitrate, about 2 percent by weight of acrylonitrile, 0.75 to 1 percent by weight of nitromethane and about 0.25 percent by weight of a butene oxide, all percentages being based on the weight of the l ,1 l-trichloroethane.

Claims

2. A composition as claimed in claim 1 wherein the ester has a boiling point at normal atmospheric pressure which does not exceed 130* C.
3. A composition as claimed in claim 1 wherein the ester is isopropyl nitrate.
4. A composition as claimed in claim 1 wherein the ester is selected from the group consisting of methyl nitrate, ethyl nitrate and 2-ethoxyethyl nitrate.
5. A composition as claimed in claim 1 wherein the amount of said esters is 1 to 4 percent by weight of the 1,1,1-trichloroethane.
6. A composition as claimed in claim 1 wherein said composition additionally contains from about 0.5 to 10 percent of the weight of the 1,1,1-trichloroethane of one or more members selected From the group consisting of acetonitrile, acrylonitrile, propionitrile, dimethoxyethane, isobutanol, tertiary butanol, tertiary amyl alcohol, ethyl acetate, isopropyl acetate, ethyl methyl ketone, nitromethane and nitroethane.
7. A composition as claimed in claim 6 wherein the proportion of the said members is within the range of 0.5 to 4 percent by weight of the 1,1,1-trichloroethane.
8. A composition as claimed in claim 6 wherein the combined components other than 1,1,1-trichloroethane represent more than 4.5 percent and less than 10 percent by weight of the 1,1,1-trichloroethane.
9. A composition as claimed in claim 1 wherein the composition contains 0.1 to 2 percent of the weight of the 1,1,1-trichloroethane of aliphatic epoxides containing 3-6 carbon atoms per molecule.
10. A composition as claimed in claim 1 wherein the composition contains 0.1 to 1 percent of the weight of the 1,1,1-trichloroethane of one of the isomeric butene oxides or a mixture of the said isomers.
11. A composition as claimed in claim 1 wherein the amount of said esters of nitric acid is 2 to 4 percent by weight of the 1, 1,1-trichloroethane and which contains additionally 0.5 to 4 percent of acrylonitrile and 0.1 to 1 percent of butene oxides calculated on the weight of the 1,1,1-trichloroethane.
12. A composition as claimed in claim 11 which contains additionally 0.5 to 2 percent by weight of the 1,1,1-trichloroethane of nitromethane or nitroethane.
13. A composition claimed in claim 11 which contains additionally 0.5 % to 4 percent by weight of the 1,1,1-trichloroethane of one or more members selected from the group consisting of dimethoxyethane, isobutanol, tertiary amyl alcohol, isopropyl acetate and ethyl methyl ketone.
14. A stabilized solvent composition which comprises 1,1,1-trichloroethane, about 3 percent of its weight of isopropyl nitrate, about 2 percent of its weight of acrylonitrile and about 0.25 percent of its weight of butene oxides.
15. A 1,1,1-trichloroethane composition consisting essentially of 1,1,1-trichloroethane and from 0.5 to 10 percent by weight of the 1,1,1-trichloroethane of an alkyl ester of nitric acid which contains less than 5 carbon atoms per molecule and from 0.5 to 10 percent by weight of the 1,1,1-trichloroethane of one or more members of the group consisting of acetonitrile, dimethoxyethane, tertiary butanol, ethyl acetate, nitromethane and nitroethane.
16. A composition as claimed in claim 15 wherein the proportion of the said members is within the range 0.5 to 4 percent by weight of the 1,1,1-trichloroethane.
17. A 1,1,1-trichloroethane composition consisting essentially of 1,1,1-trichloroethane and from 0.5 to 10 percent by weight of the 1,1,1-trichloroethane of an alkyl ester of nitric acid which contains less than 5 carbon atoms per molecule and 0.1 to 1 percent by weight of the 1,1,1-trichloroethane of butene oxide as stabilizers for the 1,1,1-trichloroethane.
18. A composition which consisting essentially of 1,1,1-trichloroethane, about 2 percent by weight of isopropyl nitrate, about 2 percent by weight of acetonitrile, about 1 percent by weight of nitromethane and about 0.25 percent by weight of butene oxide.
19. A composition as claimed in claim 6 wherein the composition contains 0.1 to 1 percent of the weight of the 1,1,1-trichloroethane of aliphatic epoxides containing 3-6 carbon atoms per molecule.
20. A composition as claimed in claim 19 wherein the composition contains about 2 percent by weight of isopropyl nitrate, about 2 percent by weight of acrylonitrile, 0.75 to 1 percent by weight of niTromethane and about 0.25 percent by weight of a butene oxide, all percentages being based on the weight of the 1,1,1-trichloroethane.