Safe Handing and Storage of Organic Peroxides in the Labloratory DAVID C. NOLLER anti DOUGLAS J. BOLTON lucid01 Division, Wallace & Tiernan, Inc., 1740 Milifary Rd., Buffalo 5,
b Proper and safe methods for handling, storage, arid disposal of laboratory quantities of organic peroxides are discussed. The safety characteristics of some peroxides are tabulated from data derived from the specialized tests described. Methods are given for the detection and removal of residual or trace quantities of peroxides as well ai; precautionary measurements to be followed in their purification. A brief discussion of some physiological aspects is included.
T
COMMERCIAL USE of organic peroxides has increased markedly over the past 20 years, particularly in the plastics industry. Not only has the actual consumption increased, but because of the variations in the technology of their applications, it has been necessary to synthesize many new peroxides. K i t h this growth, the chemist in the analytical and research laboratory has been faced with tb: problem of the safe storage and handlirg of many different kinds of peroxidic c3mpounds. It is good practice to handle any organic peroxide with respect; houever, the extremely liazardous characterihcs of a relativcly fe\$ peroxidic compounds should not brand all commercial products as dangerous. The purpose of this paper is to dispel certain fears and misstatements regarding organic peroxides and elucidate the hazards connected with their presence in the laboratory. HE
HANDLING, STORAGli, SAMPLING, AND DISPCSAL
Handling. I n the handling of organic peroxides, emphasis is placed on precautionary measures. Some of the following are more specific for peroxides while others are common laboratory practices, b u t all should be observed when h,zndling organic peroxides. Wear safety glasses or face shields at all times. Carry out handling operations behind safety shields and/or in hoods with safety glass. Restrict the quantities to be handled to the minimum amount required. -4ny material not immediately needed should be returned to the storage area.
N. Y .
Clean up all spillage immediately and destroy according to the recommendations given in the section on disposal. Meticulously clean all equipment. hiany peroxides are sensitive to contaminants such as strong reducing or oxidizing agents. Do not allow smoking, open flames, etc., in the vicinity of peroxides. Place fire extinguishers within easy reach. Wash with soap and water in case of contact with the skin. Flush eyes immediately with copious amounts of water in case of accidental splashing. Store sample quantities in the manufacturers' original containers. Samples taken from larger quantities should be transferred to glass or polyethylene bottles. Follow safety recommendations provided by the manufacturer (labels, data sheets, etc.). Do not dilute peroxides indiscriminately. For example, some cyclohexanone peroxide structures dissociate in solution forming hydrogen peroxide as one of the products. If acetone is used as a solvent, there could be a possible interaction with hydrogen per oxide forming shock sensitive acetone peroxides. Concentration of the mixture could cause crystallization of these acetone peroxides creating an explosion hazard. -4 similar condition would exist with the acetone dilution of some methyl ethyl ketone peroxide formulations containing hydrogen peroxide.
Storage. The temperature a t which a peroxide should be stored is regulated by its thermal stability and physical form. T o maintain the nctive oxygen content and catalytic activity of some peroxides, it is necessary t o use refrigerated storage. Certain minimum temperatures must be observed, however, t o prevent the crystaliization of hazardous peroxides froin solution. For example, pure acetyl peroxide which is extremely shock sensitive will crystallize from the dimethyl phthalate diluent below 0' C. (32' F.). The irnportancc. of storage space set mide solely for organic: peroxides cannot be overemphasized. Ideally, all laboratory quantities 4iould he stored under refrigeration. The shelflife of all peroxides stored in the cold is materially lengthened, making this practice a must for analytical control
samples. This should be done even though some peroxides, such as benzoyl peroxide and di-t-butyl peroxide are very stable at room temperature. Explosion-proof or standard refrigerators that have been converted should be used for peroxide storage. This conversion can be accomplished by locating all controls on the outside, removing the door switch and the inside light and sealing the holes. Magnetic door latches are also advisable. One manufacturer now modifies household type refrigerators a t a nominal extra cost through a local distributor. Peroxides should be kept away from all sources of heat such as radiators, steam pipes, and the direct rays of the sun. It is also good practice to protect peroxides from light which causes decomposition of some peroxides. Strong reducing agents, such as cobalt naphthenate, tertiary amines, and mercaptans or oxidizing agents, such as concent'rated mineral acids should never be stored in close proximity to organic peroxides. Accidental contamination due to breakage or spillage in a confined area such as in a refrigerator could result in a n explosive decomposition. Inventories should be examined periodically and old samples destroyed as recommended under the section on disposal. Sampling. Sample quantities should be stored in t h e original containers. Samples of liquids from bulk packages shouId be transferred to glass bottles with vented closures or polyethylene containers (where practical). Solids should be tra.nsferred t o polyethylene or polyethylene-coated fiber containers. Never use glass bottles with screw caps or glass stoppers. Granules of frictionsensitive peroxides-o.g., benzoyl peroxide, succinic acid peroxide-trapped in the cap or bottle threads would present a hazard. Disposal. Disposal of organic peroxides has been covered in a comprehensive article dealing primarily with large quantities ( { I ) and the ensuing discussion has been designed t o conform to laboratory requirements. In general, any spilled, contaniiriated, or overage samples should be absorbed (liquids) or blended (solids, pastes) with generous quantities of noncomVOL. 35, NO. 7, JUNE 1963
* 887
Table I. Summary of Safety Test Data
Solid rand Paste Peroxides bpid Burning hesting rate c. (see.) Product explodes 1-2 Benaoyl peroxide low102 rapid dec. does not bum Benzoyl peroxide (m,et-25% unless water 109-112 water) evaporates rapid dec. 30 Benzoyl peroxide (50% paste 87-91 with trieresyl phosphate) rapid dec. burn8 with 2,4-Dichloroheneoyl peroxide 81-82 difficulty (50% paste with dibutyl phthalate) rapid dec. 660 Lauroyl peroxide
-
Shock sensitivity L.P.D. (Bureau tester) class I11 sensitive 3-4"
not sensitive
IV
not sensitive
111
not sensitive
IV
not sensitive
IV
not sensitive
IV
sensitive 6'
IV
83-85
Decanoyl peroxide Bis( 1-hydroxycyelohexyl) peroxide Cyclohexanone peroxide (85% solid with dibutyl nhthalate) 2,5-Dimethylhexyl-Z,Mi(peroxybenzoate) Succinic acid peroxide
420
1170
rapid dec. IO?
sensitive
I11
420
rapid dec.
not sensitive
IV
8
rapid der.
sensitive 4"
IV
SAFETY TESTING
All organic peroxides in the research, pilot plant or production stage are screened in a program of safety and stability tests. The results of these tests are taken into consideration in the decision to send out laboratory samples for evaluation or before going into commercial production. The data obtaiued determine the form or concentration in which a particular product is marketed. The tests are described briefly and a summary of the test data ANALYTICAL CHEMISTRY
104
650
bustible inert substances such as perlite or vermiculite and burned. Quantities of 1 ounce or less may be burned in a laboratory hood behind a safety glass shield. Larger amounts should be burned in a trench dug in an isolated area. I n a congested metropolitan area where burning is impractical or unlawful, chemical hydrolysis can be employed. Diacyl peroxides can be conveniently destroyed by cautious addition to approximately four times their weight of a well stirred, cold, 10% sodium hydroxide solution. The ketone peroxides, hydroperoxides, and peroxyesters are much more resistant to alkaline decomposition, and require 10 times their weight of ZOyo sodium hydroxide and longer stirring periods. Peroxides, like most other flammable liquids, have limited solubility in water and therefore should never be disposed of by flushing down sink drains to a sewer.
888
mild der. 75-76 mild dec.
3-5"
128
120
obtained for a number of commercially available peroxides is found in Tnbles I-IV. The following is a list of these tests, some of which are modifications of those used by the Bureau of Explosives to determine the acceptability of peroxides for shipment in interstatc commerce: Burning Rate, Heat Sensitivity (Rapid Heating Test), Flash Point (Micro Open Cup), Shock Sensitivity, Lead Pipe Deformation, and Thermal Stability Testing. Burning Rate. The rate at which peroxides burn varies considerably. The burning rate of solid or paste peroxides is measured by igniting a 20-gram sample distributed uniformly over 20 inches i n a V-shaped metal trough and noting the time and intensity of burning. Note from Table I that dry benzoyl peroxide burus in 1 to 2 seconds whereas a 50% paste of the peroxide with a plasticizer requires 30 seconds. Consequently, dry benzoyl peroxide should never be disposed of by burning unless it has been blended with a large quantity of a noncombustible substance (perlite, vermiculite). Liquid peroxides are tested bv igniting a I-gram sample in a porcelain dish (40 X 10 mm.) and noting the ease or difficulty of ignition plus the time and nature of burning. Most liqnid peroxides ignite readily and burn evenly for a period and then they emit intermittent flashes when the decomposition temperature is reached. Those peroxides incorporating a volatile solvent will burnevenlyuntil most of the diluent is consumed and then burn vigorously.
Figure 1.
Rapid heoting
test op-
paratus
Data from these tests are listed in Tables I and 11. Heat Sensitivity (Rapid Heating Test). The heat sensitivity of peroxides is an important property in regard t o their possible hazardous nature. For each peroxide, a temperature exists at which it will begin to decompose, the nature and rate of which denend on the n e r o d c in question. The test involves the controlled heating a t a rate of 4" C. per minute of a I-gram sample in a test tube (Figure 1j . The temperature and type of decomposition are noted. To allow for comparison, the following terminology has been adopted and used to report the data in Tables I and 11. Explodes. Complete decomposition takes place snddcnly with generation of appreciable force nnd/or smoke, fumes, or report-e.g., benzoyl peroxide, tbutyl peroxyacetate.
Rapid Decomposition. Decomposition t&es place suddenly, usually with evolution of smoke, fumes, and a puff or mild report-e.g., paste of benzoyl peroxide and tricresyl phosphate. Mild Decomposition. Slow decomposition accompmied by evolution of vapor and/or discoloration of s a m p l e e.&, methyl ethyl ketone peroxide solutions. Refluxes. No visual signs of decomposition; peroxide refluxes on sides of test tube and eventually distills offe.&, di-t-butyl peroxide. The data obtained are used as an aid in the selection of safe operating conditions when using organic peroxides. Flash Point. Flash points of liquid organic peroxides and peroxide solutions are determined mainly t o aid in their flammability classification for shipping purposes-i.e., whether Red label (flammable material) or Yellow label (oxidizing material) designation. The flash point procedures ordinarily used for flammable liquids (ASTM Dl310, ASTM D92) make use of a large size sample and the results depend upon the vapor pressure of the volatile constituents. With organic peroxides, one also has to consider seriously the beat sensitivity of the material and the possibility of a hazardous exothermic decomposition. For this
Figure 2. Micro open cup flash point apparatus
Table II. Summary of Safety Test Data
Liquid Peroxides Burning Rapid Micro cpen rate heating cup flash Product (see.) "C. point O F . Acetyl peroxide (25% in di5 mild 175-180 methyl phthalate) explosion 90-92 t-Butyl peroxypivalate (75% 61 rapid dec. 155-160 in mineral spirits) 72-73 t-Butyl peroxyacetate (75% in 18 explodes 70-i5 benzene) 158 &Butyl peroxyisobutyrate ( i 5 % 38 rapid dec. 75-80 in benzene) 88 &Butyl peroxybenmate 33 mild dec. >I90
Shwk sensitivity L.P.D. (liquid tester) class not sensitive I11 not sensitive
I11
not sensitiw
111
not sensitive
IV
not sensitive
111
111
Di-&Butyl peroxide
34
refluxes 100 on
70-75
not sensitive
I11
t-Butyl hydroperoxide-iO%
30
refluxes
100-105
not sensitive
IV
95 on refluxes 120 on mild dec.
130-135
not sensitive
IV
185-190
not sensitive
111
&Butyl hydroperoxide90%
20
2,5-Dimethyl-2,5-di(t-butylperoxy)hexane
90
140-150
Methyl ethyl ketone peroxides (60% in dimethyl phthalate) LupersoP DDM 55 mild dec. 125-130 not eensitive 135 Lupersol Delta 7 5 mild dec. 140-145 not sensitive 135-140 Lupersol Delta-X 90 mild dec. 175-180 not sensitive I40 a Registered tmde mark, Lueidol Division, Wallace & Tiernan, Snc. reason an aluminum micro open cup of 5-ml. capacity is used. The relative size of the micro and conventional open cups can he seen in Figure 2. Flash points of nonperoxidic materials are in close agreement with reported values, using the Cleveland Open Cup apparatus, in the 100" t o 200" F. range; however, some variances are noted for compounds flashing below 100°F. The flash points of representative liquid peroxides are listed in Table 11. Shock Sensitivity. Susceptibility to impact. or shock is measured with an apparatus which allows the dropping of a known weight through a known distance on a standard size sample. Figure 3 shows the shock tester used for liquid samples on the left, and the Bureau of Explosives Impact Apparatus, used for solids, on the right. Sensitivity is determined by noting smoke, report, odor of decomposition, or evidence of physical deterioration of the sample. Granular benzoyl peroxide is a standard for solid and paste peroxides and all commercially available peroxides are diluted, if necessary, to be less shock sensit.ive. Table I shows this quite clearly. Several of the commercial products in Table I1 contain dilnents to reduce or eliminate the shock sensitivity of the pure or concentrated peroxide.
111
SI1 111
Lead Pipe Deformation (L.P.D.)
Test. This shock sensitivity test is a slight modification of the test originally reported by Shanley (11). I t involves the use of a #S EB-IO blasb ing cap (Hercules Powder Co.) immersed in a 10-gram sample of peroxide in a test tube which fits snugly in a lead pipe of standard dimensions. The lead pipe assembly is placed in a protective enclosure and the cap detonated from a safe distance. Data are recorded on the type of deformation and/or damage to the pipe. For piirposes of evaluation the following standards were set up as shown in Figure 4. L.P.D. Class Standard I Picricacid Ammonium nitrate
I1
I11 Benzoyl peroxide
IV
Water
Remarks The pipe is fragmented. Pipe is severed: at the point of severance there is a noticable flaring of the lead. The pipe is bulged and ruptured but not severed. The pipe. ie deformed or bulged with some lead scaling.
The data from these tests are listed in Tables I and 11. None of our comVOL. 35, NO. 7,JUNE 1963
a89
Figure
~
3. Shock
sensitivity apparatus
~~
Table 111.
Summary of Thermal Stability Data
Solid and Paste Peroxidea
Praduot Benzoyl peroxide Benzoyl peroxide (wet-25% water) Benzoyl peroxide (60% paste with tricresyl phosphate 2,4-Dichlorobenzoyl peroxide (50% paste with dibutyl phthalate) Lauroyl peroxide Decanoyl peroxide Bis( I-hydroxycyclohexyl) peroxide Cyclohexanone peroxide (85% solid with dibutyl phthalate) . . 2,5-Dimethyl hexyl-2,5-di(peroxybenzoate) Succinic acid peroxide
890
.
ANALYTICAL CHEMISTRY
750 c. (167' F.) tests
% Loss active oxygen after 1 month30" C. 40" C. (86"F.) .
(104" .
F.)
Recommended storage temp.,
optimum
' F. 68-86
passed passed passed
stable stable stablc
stable stable 5-7
68-86 50
passed
3-10
13-21
50
passed fails fails
0-1 3 e-3
2-3 74 2,948
50
fails
0-1
50
(oven) passed
2.5
stable
stable
G8-86
passed
2
2
50
50 50
mercially available organic peroxides is rated as hazardous as Class 11. Thermal Stability Tests. 30' C. (S6O F.) and 40" C. (104" F.). Samples of solids and pastes (25 t o 50 grams) and 25 t o 50 ml. of the liquid peroxides are placed in suitable glass containers, stored at the two temperatures, and assayed weekly for at least 1 month. Thermostated ovens or water baths may be used. Peroxides requiring refrigerated storage are observed at selected lower temperatures. The results of these tests (Tables 111 and IV) are used to make recommendations regarding storage temperatures and shelf-life. The optimum temperatures given are those which allow for reasonable stability of catalytic activity and active oxygen content. The very marked decrease in stability should he noted for decanoyl peroxide (Tahle 111) between 30' and 40" C. Consequently, the storage temperature recommended is 10' C. (50" F.). The stability of t h u t y l peroxypivalate and &butyl peroxyisohutyrate solutions (Table IV) at 20" and 30' C. are such that storage temperatures of -1" C. (30" F.) and 10" C. (50" F.), respcctively, are recommended. 75" C. (167" F.) Water Bath and Water Jacketed Oven Tests. These tests represent an extreme temperature condition during shipment and storage. A 10-gram sample, in a loosely-stoppered tube, is placed in a shielded 75" C. water bath until decomposition takes place or for a maximum of 48 hours. If an explosion or vigorous decomposition occurs, the test is considered a failure. If the sample melts and/or decomposes mildly over the period, it bas passed the test and is assayed to determine the per cent active oxygen loss. If the sample passes the water bath test, the same procedure is repeated in a 75" C. water jacketed oven equipped with an explosion venting door. Any other type of nousparking oven can be used. The results of this oven test may differ as the cooling effect of the water bath is absent. DETECTION A N D REMOVAL OF RESIDUAL PEROXIDE CONTENT
It is often desirable t o have knowledge of chemical and physical means for detection and removal of residual peroxidic content. Many fires and explosions have been reported (9) in the final stages of evaporation and distillation of easily-autoxidizable solvents such as ethyl and isopropyl ether, dioxane, and tetrahydrofuran which could have been avoided iS a simple qualitative test for peroxide content had been carried out. Detection. Hydroperoxides, peroxy acids, diacyl peroxides, and most
peroxyesters are readily reduced and can be detected by acidifying a small sample (1 t o 2 ml.) with glacial acetic acid followed by cautious addition of a saturated sodium or potassium iodide solution. An evolution of iodine (rapid development if hydroperoxides are present) is indicative of peroxide reduction. Application of heat may be necessary in the case of the more difficultly redncihle peroryesters. Ferrous thiocyanate (ferrous ammonium sulfate plus ammonium thiocyanate) is often substituted for the inorganic iodide where extremely small peroxide concentrations (as low as 15 pg.) are involved. A rapid colorimetric determination of microgram anionnts of lauroyl and benzoyl neroxides has been reccntlv published-(4). Dialkyl and alkylidene peroxides undergo- reduction only under rnther vigorous conditions. A method commonly employed requires treatment of an acidified sample with hydriodic acid followed by heating a t 60" C. until iodine evolution is evident. The common physical methods of identication-i.e., gas and liquid phase chromatography, ion exchange, polarography, and absorption (ultraviolet, infrared) spectrometry have also been
Table IV.
Product Acetyl peroxide (25% in dimethyl phthalate) &Butyl peroxypiva1st.e. (75% in mineral spirits) &Butylperoxyaeetste (75% in benzene) &Butylperoxyisobutyrate (75% in benzene) 1-Butyl peroxybeneoate Di-&Butylperoxide t-Butyl hydroperaxidc-
detail hv Davies (3).
75" c. (167" F.) tests
% Loss active oxygen
Recommended
-after 1 month-
40' C. (104" F.)
30°C.
(%OF.)
fails (oven) fails
9-11
31-35
14% a i 20- c.
unstable
passed
stable
stabls
6X-86
passed
28.7
48 3
50
passed
stable
0-2
GO
6&80
passed
stable
passcd
stable stable
... ...
68-86 68-86
passed
stable
stable
slnl,lc
32
0
41
0-30
(0%
1-Butyl hydroperoxide-
68-86
90%
passed 2,5-Dimethyl-2,6-di(tstable butylperoxy) hexane Methyl ethyl ketone peroxides (60% in Lupersol DDM passed stable Lupersol Delta. passed stable Lupersol DelteX passed stable
emnlnvPd and -.SPP rliac31rserl in anma -... r _ _ i i _-.._ _._ I"..." _.lllll"l
Summary of Thermal Stability Data Liquid Peroxides
mixtures and solvents
by
careful
stable
50
68-80
dimethyl phthalate)
.. ...
50
0-2 (t?
...
50
(t-2
GO
and subsequent washings of the treated
...".._.._""
t.roat.mmt. wit,h nf .mnv matorial 7uit.h rli1nt.r n l l i a l ^i n n r l m dor ~ ... ~ . i . . " " anliit.inna ~--~"__.._.a t--.. "~ ..I"_. I"
~
alkalis. Peroside reduction by treatment with solutions of sodium sulfite, stannous chloride, lithium aluminum
CLASS 11, AMMONIUM NITRATE
have also been found t o he effective. Some of the polymeric peroxides present in autoxidized ethers are difficult t o zinc and acid, or sodium and alcohol is effective. Ferrous sulfate in 507" sulfuric acid has also been used t o advantage in some instances. Physical methods for peroxide removal are reported by Davies (S) and Hawkins ( 6 ) . Solvents or monomers susceptible to autoxidation should be stored in full, air-tight, amber-glass bottles, preferably in the dark. Various substituted phenols and aromatic amines have proved to be effective inhibitors-e.g., 0.1 mg. of pyrogallol in 100 cc. of ether prevented peroxide formation over a %year duration (a). Ethers stored over certain anion exchange resins remain essentially peroxide-free indefinitely. METHODS FOR ORGANIC
PEROXIDE PURIFICATION
CLASS IV, WATER
letormatian test stanaarus
The analytical or research chemist often finds it desirable to have small quantities of organic peroxides on hand io higher pnrities than are commercially :Ivailable for wntwl stnndards, kinetic studics, etc. 111 general, the prescribed Ivoccdiires used for purification of organic solids and liquids apply to peroxides with several variations. Recrystallization. Organic peroxides are sensitive t o excessive or VOL. 35, NO. 7, JUNE 1963
891
prolonged heating as shown in the preceding portion of this paper, and t h e use of a low boiling solvent or mixture of solvents will usually allow solution a t room temperature. If heating is required, a thermostatically controlled heating bath should be used. Where absolute purity is not critical, use precipitation methods because such operations can be performed at ambient or cold temperatures. Benzoyl peroxide, 997c pure, as an example can be precipitated from an acetone solution with the addition of cold water. If it is desired to operate under anhydrous conditions, the peroside can be precipitated from a chloroform solution with an excess of cold absolute methanol. Other safe methods for benzoyl peroxide purification have been described (8, I O , 12). Distillation. Although i t is possible to concentrate or purify several liquid peroxides by distillation, this is in general a haza,rdous undertaking. It should be considered only after a thorough study of the peroxide in que,3tion. Perosides t h a t are shock sensitive whcii pure should not be distilled. All distillation of liquid organic peroxides should be carried out under reduced pressures as the majority of commercially available peroxides decompose well below their boiling points at atmospheric pressures. At least one, and preferably two, cold traps should be included in the system to prevent peroxide contamination of the vacuum pump oil. As an extra precaution, the oil should be changed a t frequent intervals, where repeated distillation or stripping is involved. I’ressure ranges should be selected so that boiling takcs place well below the dccoinposition temperature. .2lthough reportedly t-butyl peroxybenzoate can be distilled safely a t temperatures below 100’ C. and a t very low pressures, an explo5ion occurred during a distillation a t 115” C. and 4 mm. ( I ) . I t should be noted that the decomposition tempera-
Table
V.
ture of the peroxide, 111’ C. (Table 11): was exceeded. A common practice is to dilute thc peroxidic compound with a large volume of an inert high boiling liquid to ensure adequate heat dissipation. Perosides should not be distilled from their dilueiits or plasticizers as these have been added t o make a shock sensitive material safer commercially-e.g., do not distill the methyl ethyl ketone perosides from their solution in dimethyl phthalate. .A few perosides liave been distilled a t atmospheric pressure; however, reduced pressures are definitely recommended as the crude product in the still pot may undergo vigorous induced decomposition. Avoid concentrating peroxidic residues in the still pot. Distillation may also be carried out in an atmosphere of inert gas-e.g., nitrogen. PHYSIOLOGICAL ASPECTS
Effect on Eyes. Kuchle ( 7 ) and Floyd (5) independently investigated the effects of several perosides on rabbit eyes, and Zielhaus (14) summarized these data in tabular form, a portion of n-hich appears in Table V. These data show that methyl et,hyl ketone peroside and cumene hydroIleroside are injurious even in dilute solutions. Di-t-butyl peroside, lauroyl peroxide, and benzoyl peroxide viere found to have only a mild irritating effect. There is no substitute for thorough and immediate flushing with water. Oils or ointments should not be used as they tend to “seal in” the irritant. Kuchle found that flushing after 4 seconds resulted in little or no damage. .\ftcr 30 seconds, flushing still had a Iieneficial effect, but after 60 seconds it had no effect. I t is rc-emphasized that safety g l a w s or face shields should always be worn when handling peroxides. Effect on Skin. Organic peroxides may have a local corrosive or irritating
Effect of Various Organic Peroxides on Rabbit Eyes
Form and concentration a t application Tec*hnicalpowder 937’ Powder Technical liquid Commercial 75Y0 solutionb 35% in Propylene glycol 7 yoin Propylene glycol Cumene hydroperoxide Commercial 70% liquidb l0Toin Propylene glycol 1yoin Propylene glwol Methyl ethyl ketone 47’ in Dimethyl phthalate 0.6% in Dimethyl phthalate peroxide Eyes flushed after 60 sec. L = slight, temporary damage. S = severe, permanent damage. * Commercial liquid used for diluted concentrations.
Peroxide Lauroyl pernxide Benzoyl peroxide Di-t-butyl peroxide t-Butyl hydroperoxide
0
892 *
ANALYllCAL CHEMISTRY
Effrcta I, X X X
...
... X
. .
. . X
. . X
-.
s
...
...
... X X
... X X ... X
...
effect on the skin and contact should be avoided. Prolonged contact may lead t o increased sensitivity with the formation of a rash. Methyl ethyl ketone peroxide solution and hydroperoxides exhibit more pronounced irritant properties. Prolonged exposure is accompanied by a burning sensation. Cyclohexanone peroside may cause a rash, especially to persons with sensitive skin. Benzoyl peroxide paste formulations exhibit no particular irritating effect. Because of the corroyive effect of some, any peroxide coming in contact n-ith the skin should be promptly and thoroughly washed off with soap and water. If necessary, an ointment or lanolin may be applied in cases where burns or a rash have developed. Contaminated clothing should be removed and laundered before reusing. Inhalation. Peroxide vapors may cause irritation of the eyes, nose, and throat and in high concentration cause inebriation similar to the effects of alcohol. If over-exposure occurs, remove the victim to fresh air and call a physician. Prevent the accuniulation of hazardous vapor by performing all operations in a hood. The t-butyl perosyisobutyrate and t-butyl pcrosyacetate solutions should he handled in this manner becanse of the tosic vapors of benzene. These peroxyesters have recently been made available in mineral spirits solution to eliminate the hazard of benzene. General Toxicity Studies. The majority of the reported toxicological studies deal mainly with nonperoxidic compounds and mention one or two organic peroxides. Of the few articles dcaling esclusirely with organic peroxides, Floyd and Stokinger’s study ( 5 ) of the effects of four compounds b>r oral, intraperitoneal, skin, and eye administration to rats and mice is quite comprehensive. Methyl ethyl ketone peroxide solutions were shown to be more toxic than t-butyl hydroperoside and cumene hydroperoside. They were locally corrosive on the mouth, pharynx, esophagus, and gastrointestinal tract. Di-t-liutyl pwoxide had little or no toxic effecta. No human fatalities from accidental ingestion have been reported. The Summary Tables of Biological Test.; contain data on organic peroxid(,> \\-hicli \\-ere tcsttd by intraperitoncd injections in inice (13). These studies indicate that organic peroxides, in general, are not highly tosic chemicals. CONCLUSIONS
This paper has been presented to acquaint the laboratory chemist with tlie safety cliaracteristics of a numlm of commercial organic peroxides. Kecommendations have bccn niutle regard-
ing their handling, storage, disposal, and purification. Data have been presented t o enable the comparison of some commercial products on the basis of safety and stability tests. Physiological aspects have also been considered briefly. It has been shown that the potential hazard varies considerably, but the proper application of the safeguards and precautions described in this paper, in data sheets, and on product labels, enables one to use safely any commercial product. It is the responsibility of each laboratory to see that personnel handling peroxides are fully aware of their properties. It is emphasized t h a t one cannot generalize in regard to safety characteristics of organic peroxides. Each product should be considered separately and thoroughly from :t11 aspects before use.
ACKNOWLEDGMENT
The authors express their appreciation to A. I. Andrew, 0. L. llageli, and K. L. Ditzel, Lucidol Division, Wallace &- Tiernan, Inc., for reviewing the manuscript and offering helpful suggestions. LITERATURE CITED
(1) Cfiegee, R., Angew. Chem. 65, 398 (1953). (2) Davies, A. G., J . Royal Znst. Chetnistry 80, 38G (1066). ( 3 ) Davies, i\. G., “Organic. Peroxides,’’ Butteraorth, London, 1961. (4) Dugan, P. K., AKAL.CHEM.33, 696 (1961). (5) Floyd, E. P., Stokinger, H. E., Am. Ind. Hygiene Assoc. J . 19, No. 3, 205 (1958). (6) Hawkins, E. G. E., “Organic Per.
oxides,” E. and F. F. Spon Ltd., London, 1961.
( 7 ) Kuchle, H. J., Zentr. f u r drbeitsmed, Arbeitisschutz 8 , 25 (1958).
(8) Lappin, G. R., Chetn. Eng. A‘ews 2 6 , 3518 (1948). (9) “Organic Peroxides-Their Safe Handling and Use,” Bdletzn 30.40, Lucidol Division, Wallace & Tiernan,
Inc. (lO)Pfat, J., Adem. Sew. Chim. Etat (Paris) 34, 385 (1948). (11) Shanlev, E. S., Greenspan, F. P., Ind. Eng.”Chem. 39, 1536 (1Y4T). (12) Taub, D., Chern. Eng. News 27, 46 (1949). (13) “Summary
Tables of Biological TePts,” Chemical-Biological Coordination Center, fational Research Council, Washington 26, D. C. 2 , 241, 244, 302
(1950): 4 , 103, 110 (195%); 8, 653 (1956). (14) Zielhaus, R. L., Plaatzca 13, 1122 (1960). An abstract of this article may
be obtained from the Luridol L)ivision, Wallace &I Tiernan, Inc., BulLetzn 20.17.
RECEIVED for review December 7 , 1962. Accepted April 1, 1963. Division of Analytical Chemistry, 142nd Meeting, ACS, Atlantic City, N. J., September, 1962.
ControlIecI- Potentia I Co u I omet ric Dete rmI nat I o n of Hydrogen Peroxide J. E. HARRAR Chemistry Division, Lawrence Radiation laboratory, Universify o f California, livermore, Calif.
b A procedure has been developed for the determination of hydrogen peroxide b y controlled-potential coulometry, The method involves the oxidation of hydrogen peroxide a t a platinum electrode a t +0.93 volt vs. S.C.E. in a supporting electrolyte of 1M sulfuric acid; a complete electrolysis requires 3 to 4. minutes. Moderate amounts of many cations, common organic stabilizing agents, peroxydisulfate ion, and chlcwide ion do not interfere. Chloride ion, however, increases the time of this electrolysis, as do Ti(IV) and V(V) which complex hydrogen peroxide. The analytical technique i s influenced b y the fact that the heterogeneous, catalytic decomposition of hydrogen peroxide a t the platinum electrode at open circuit is nearly as rapid as the electrolytic oxidation. In the range of 0.1 to 2 mg. of hydrogen peroxide in a solution volume of less than 5 ml., the relative standard deviation of the determination is 5 0.1
yo.
T
HE ANODIC decompo,ition of hydrogen peroxide in solution to form oxygen has been a subject of continuing attention for over a cer tury, and it was very early demonstrattld that the passage of two faradays 0’ electricity produced the cvolution of one mole of
oxygen (14). Interest in the mechanism of the reaction, its relationship to the heterogeneous, catalytic decomposition of hydrogen peroxide, and the influence of the surface condition of the electrode has resulted in a large body of electrochemical data. Recent voltammetric investigations (3, 6, 18), particularly those of Hickling and Wilson (Y),have indicated that the Oxidation of hydrogen peroxide at a platinum electrode could form the basis of a direct coulometric determination of this substance. Accordingly the present work was undertaken to establih the conditions requisite to a n accurate, precise, and rapid controlled-potential coulometric method. While many media may be suitable for such a determination (Y),acid solutions were chosen as the supporting electrolytes for their convenience and previous satisfactory coulometric performance; sulfuric acid mas the medium of most of the inve.tigation, although perchloric and nitric acids appeared to be equally sati>factory in early work. Attention has been given to the role of the heterogeneous decomposition of hydrogrn peroiide, nhose rate has been reported to approach that of the electrolytic oxidation (3, 12). Evidence that the state of surface oxidation cf platinum electrodes influences the oxidation procse5s (3, 7, IS) and present
knowledge of the behavior of platinum surfaces under oxidizing conditions (1, 2,10,1S) have directed efforts toward defining the effect of thi, variable on the analytical results. EXPERIMENTAL
Apparatus. T h e controlled-potential coulometer used in this study was a n operational-amplifier type instrument designed in this laboratory ( 1 7 ) . The integrator was calibrated electrically and its readout voltages m r e measured with a Son-Linear Systems Model 481 digital voltmeter. Voltammetric measurements were made with a n ORKL hlodel Q-1988 controllcd-potential and derivative polarograph (9). The electrolysis assembly was similar to that described by Yhults ( 1 6 ) . The cell consisted of a glass tube, 25-mm. i.d. by 50 mm. long and tapered a t the bottom to a Teflon-plug sto1)coclc for drainage. h Teflon cell cap held the two salt-bridge tubes and was drilled with holes for sample introduction, a wire connection to the gauze electrode, and a glass paddle-type stirrer. The analytical elrctrode for the coulometric studies was a cylindrically shaped double thickness of 45-mesh platincm, 35 mm. high and 55 sq. em. in unl’oldrd planar area. I t mas positioned concentric with the electrolysis vessel and outside the salt-bridge tubes. The stilt-bridge tubes were obtained from VOL. 35, NO. 7, JUNE 1963
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