Handling of Chemicals that warning labels for agricultural pesticides are uniform throughout the United States. Although the Manufacturing Chemists’ Sssociation program is directed primarily to the labeling of industrial chemicals, the principles are generally applicable to small package labeling and experimental samples. However, as the repackaging of chemicals into smaller units was beyond the control of the manufacturing industry and because accidents occurred from the misuse of chemicals in these small packages, state agencies became somewhat alarmed and began to consider regulations which would require labels on packages of all sizes. Accidents arising from the handling of paint removers led Illinois to follow in the footsteps of California and Oregon. I n June 1961, Illinois passed a regulation requiring warning labeling on all containers of hazardous chemicals. Members of the LAPI Committee met with representatives from the state of Illinois. with the result that LAPI principles were adopted. The Illinois regulation copies Part I of the %IC4 manual. I n the past 2 years several states have expressed the desire to draft a similar regulation controlling labeling of hazardous chemicals. It became apparent that industry’s voluntary use of precautionary labeling of industrial chemicals would not be sufficient to forestall state legislation. It m,s felt that the next best thing would be to lend LAPI Committee efforts to help the states draft uniform regulations. The International Association of Governmental Labor Officials formed a labeling conmittee, and in conjunction with the MCA group, worked out a set of model regulations to be presented at the next association meeting for use by states considering labeling regulations.
The state of New Jersey, Department of Labor and Industry, has just issued a new regulation relating to the labeling of harmful substances, which has been patterned after this proposed model bill. Future state regulations relating t o labeling of hazardous substances will probably follow this IAGLO model. The state of New York passed a labeling code which took effect August 27, 1954. The New York regulations were worked out by the manufacturers of the MCA committee and the New York State Department of Public Health. A committee of the Chemical Specialties Manufacturers Association is working on the labeling of household products and ways of applying the MCA principles. Directions for use are usually an important addition for small packages. The Chemical Specialties Manufacturers Association committee released its first paper early in July. This association has also lent its assistance to the state of Kew York in the preparation of the labeling code and to the International Association of Governmental Labor Officials in the preparation of its model regulations. Much work remains to be done, and this will be a continuing task of this committee. EDUCATIKG THE PUBLIC
There still remains an important task, that of educating the public to understand the significance of warning labels and teaching them to read the label. I n this task of education, help is needed. The Manufacturing Chemists’ Association appeals to all members of the chemical industry and their trade associations for suggestions as to how this might best be accomplished. RECEIVED for review October 1.3, 1954.
-4CCEPTED
March 25, 1956.
END OF SYMPOSIUM
I
TO IMPROVE YllELDS
1
in the Raschig synthesis of hydrazine
II
. . , gelatin three substitutes for as a metal deactivator are proposed
1I
Metal Deactivators in Synthesis of Hydrazine R. F.SkVFTNER, 33. AI. JONES, AND L. F. AUDRIETH Uniuersity of Illinois, Urbana, I l l .
T I
HE development of new potential markets requiring substantial quantities of hydrazine and hydrazine derivatives has been accompanied by intensive research designed not only to explore new synthetic approaches to this most versatile chemical commodity, but al-o to develop and improve the Raschig synthesis ( 2 , $0) making use of ammonia, chlorine, and caustic as raw materials. Chloramine is, however, the important reactant since it is produced as the intermediate from hypochlorite and ammonia, Equation 1, and then reacts under proper conditions to give hydrazine, Equation 2 . However, a side reaction, represented by Equation 3, may also take place to reduce the yield of hydrazine.
+ SaOCl + KaOH + NH, 2NH2Cl + N2Ha
XH3 SH&1
+
+ NH&1 + NaCl + + 2XH4Cl
XaOH
+ S2H4 -+
A-2
(1) H20
(2)
(3)
It has been shown that the hydrazine-chloramine reaction, Equation 3, is catalyzed by trace quantities of certain metal ions (IO),most markedly, however, by dissolved copper. To obtain satisfactory yields of hydrazine it is necessary to add to the makeu p solution a small quantity of gelatin or glue which serves as a metal deactivator. June 1955
Earlier work designed to develop, somewhat empirically, substitutes for gelatin is widely scattered in the literature; published information is summarized in Table I. This classification is based on the claimed effectiveness of these substances as inhibitors and represents a personal evaluation of the published data by the authors. The present investigation was undertaken with two major objectives in mind: 1. To develop possible substitutes for gelatin since the use of gelatin causes excessive foaming e~peciallyin the distillation of hydrazine from the salt solution which constitutes the product synthesis liquor 2 . T o arrive a t a more precise understanding of the role that gelatin and other inhibitors play in the Raschig synthesis
A standard procedure was developed to test the efficiency of a wide variety of possible metal deactivators. Complexing agents, coprecipitants, and polysaccharide derivatives were evaluated. High molecular weight proteins were in general the most effective, although a number of simple amino acids and polypeptides approached the natural products in their usefulness as metal deactivators. Experimental data indicate that those amino acids, that contain a multiplicity of sites for coordination
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and that thus serve as polydentate structures in affording opportunity for chelation, are also very effective in eliminating the damaging effect of dissolved copper on hydrazine yields. The removal of dissolved copper, presumably by coprecipitation with magnesium hydroxide and magnesium silicate also leads to higher hydrazine yields. I n a class comparable with gelatin are some commercially available derivatives of alginic acid and carrageenin. These polysaccharide derivatives are readily dispersible in the synthesis solution and serve as effective inhibitors.
Table I.
Inhibitors Evaluated for Use in Raschig Synthesis Material Group I, Yields 50%
Literature Cited +
Gelatin Albufnin Casein Animal glue Peptone Group 11, Yields 10 to 50% Trilon B Starch Glycerol Dextrin Pormaldehvde Sucrose Peptized stannic acid Flax'seed mucilage Carrageenin Soybean glue Magnesium hydroxide Manganous salts Geaweed solutions Waste lye from cellulose manufacture Hydrolysates of glue and gelatin Group 111, Yields to 10% Animal charcoal Asbestos powder Meerschaum powder Cupferron Sodium glutamate Sodium tyrosinate Sodium tryptophanate Sodium urate
Vol. 47, No. 6
the following substances were added to the test solutions: potassium ferrocyanide, potassium cyanate, ammonium thiocyanate, 8-hydroxyquinoline, thiourea, and sodium citrate. Detectable yields (about 2%) were observed when pyridine and a,a-dipyridyl were employed. Versene and Sequestrene AA were found to be relatively effective (35 to 40% yields when added in 1-gram quantities), but not as eIficient as gelatin (55 to 60% yields for 0.5-gram quantities). Additions of 0.5-gram quantities of sodium pyrophosphate, sodium triphosphate, and of sodium polymetaphosphate glass to samples of the test solution were found to have no beneficial eflect. I n view of the oxidizing character of the synthesis solution, it was considered possible that copper(II1) ion catalysis might be involved in the decomposition of hydrazine by chloramine. Stable complexes of copper(II1) with periodate and tellurate (8, 9) are known. The addition of these substances was investigated in the hope that they would interfere with any reaction involving copper(II1) as a catalyst. Both of these substances were completely ineffective as inhibitors; no detectable amounts of hydrazine were formed. This seems to make the assumption of the presence of copper(II1) as an intermediate in bringing about the reaction between hydrazine and monochloramine extremely unlikely.
EXPERIMENTAL
Procedure. Test solutions were made from 40 ml. of a 13.15M solution of aqueous ammonia, 30 ml. of a 4.2 X 10-5M solution of copper sulfate and 10 ml. of a solution of the inhibitor (or a definite weight thereof), mixed, and diluted to a total volume of 140 ml. with distilled water; GO ml. 0.4G5M sodium hypochlorite (NaOCl) were then added; the resulting solution was immediately heated and kept a t the boiling point for 15 minutes (more than sufficient time to complete the reaction). The test solution was removed from the hot plate and acidified with 50 ml. of concentrated hydrochloric acid. Aliquot samples were analyzed for hydrazine by the direct iodate method using Brilliant Scarlet (British Color Index 185) as an indicator (14). No hydrazine is obtainable from solutions containing the indicated amount of dissolved copper in the absence of gelatin. Addition of 0.5 gram of gelatin to the test solution gives hydrazine yields of 55 to GO%, based on the amount of hypochlorite used. The assumption is made that only in the presence of agents that effectively remove or reduce the dissolved copper concentration will satisfactory yields of hydrazine be obtainable. Although hydrazine can be obtained in the absence of inhibitors if highly purified reagents and equipment are employed, this condition is difficult to achieve on a technical scale. The reactants, especially caustic soda, will introduce sufficient copper t o catalyze effectively oxidation of all the hydrazine which is formed. Copper Complexing Agents and Precipitants. Compounds which had previously been shown by Audrieth and Mohr ( 1 ) to be effective deactivators in the stabilization of both dilute and concentrated hydrazine toward autoxidation were first investigated. No hydrazine was obtained when 2-gram quantities of
Figure 1. Amino acids and related compounds as metal deactivators in Raschig synthesis A. B.
Gelatin DL-histidine C. Triglycine D. Imidazole E. Ethylenediaminetetraacetic acid F.
Biuret
G.
L-arginine
I. J.
DL-a-alanine m-leucine
L.
Diglycine Glycine
H. DL-aspartic acid
K. DL-valine M.
Protein Materials. Edestin, urease, casein, lactalbumin, and pepsin were evaluated as representative protein materials related to gelatin to determine if these substances might also serve as inhibitors. All were equally effective as inhibitors and comparable with gelatin (see Figure 1, curve A for gelatin). Edestin appears to be somewhat more effective in low concentrations than gelatin. Amino Acids. Since proteins consist of aggregations of amino acid moieties, it was conceivable that one or more of the con-
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stituent amino acids might be capable of exerting a specific inhibitory action and might thus account for the effectiveness of proteins. Yields of less than 10% were obtained when 0.5-gram quantities of the following amino acids were tested for their inhibitory action: m-a-alanine, DL-valine, DL-leucine, glycine, and glycylglycine. Yields ranging from 10 to 30% were obtained when the following substances arranged in the order of increasing effectiveness were employed: DL-aspartic acid, L-arginine, and biuret. DL-histidine, and glycylglycylgfycine were found to be surprisingly effective comparing favorably with gelatin on a weight basis. Experimental data are presented graphically in Figure 1. Coprecipitating Agents. Some inhibitors function as coprecipitating agents for removal of trace metallic ions. Such deactivators remove metal ions from solution by entrapment in a gelatinous precipitate or a colloidally dispersed structure. Several silicates were precipitated in situ by the addition of the metal ion in amounts varying between 2.4 to 4.2 X lO+M to the synthesis solution containing F-Grade D u Font sodium silicate solution. The barium, cadmium, and zinc silicates were ineffective since no hydrazine was formed. Addition of aluminum ion resulted in a 15% yield; whereas, magnesium (silicate) made possible the achievement of yields approaching 50%. Direct addition of magnesium ion (as MgS04) t o the synthesis solution resulting in the precipitation of the hydroxide, likewise deactivated the dissolved copper t o give good yields of hydrazine. Saccharide Polymers. Derivatives of alginic acid and carrageenin representing high molecular weight carbohydrate m a terials are available under a variety of trade names and include such commercial types as Superloid, Kelmar, and Kelgin (alginic acid derivatives) and the Sea Kerns (carrageenin derivatives). These substances were fairly effective inhibitors. Data relating yields of hydrazine as a function of quantity of inhibitor are presented in Figure 2. Such high molecular products as polyacrylic acid, polymethacrylic acid, methylcellulose, and carboxymethylcellulose were relatively inefficient, yields of about 5% being obtained when 0.5-gram quantities were added to the synthesis solution.
line solutions such as are employed in the Raschig synthesis, is taken as a criterion. The only difference between valine and arginine is the presence of a terminal guanido group; arginine is a better inhibitor possibly because it possesses a structure which offers a multiplicity of sites for coordination. The complexing action seems to be enhanced in those instances where the amino acids are more than bidentate in character, so that chelation may take place a t several coordination sites on the amino acid structure. Higher yields of hydrazine are obtainable when such materials are employed.
DISCUSSION
Figure 2. Effectiveness of polysaccharide derivatives as metal deactivators in Raschig synthesis
I
Effective inhibitors for use in the Raschig synthesis may be placed in three distinct categories:
1. Copper complexing agents including high molecular weight proteins, some amino acids, and some of the more effective polydentate chelating agents 2. Hydrophylic colloids such as the commercially available polysaccharide polymers and their derivatives 3. Coprecipitating agents which act to remove copper ions by entrapment within a precipitate or colloidal dispersion All these classes of material remove traces of dissolved metal from solution, yet their mode of action as indicated by the classification varies decidedly. Protein materials are in effect polyelectrolytes which furnish carboxyl groups, imino and amino groups for reaction with metal ions. Such protein materials should be effective substances for the complexing of copper, and also other metallic ions, in alkaline solutions since the amino and imino groups, which constitute definite positions on the surface of the protein molecules are then free to coordinate with metal ions. Such behavior is presumably not possible in acid solution where formation of the protonated amino groups may be expected. One might therefore anticipate that amino acids in general should be more effective complexing agents for certain metallic ions in alkaline solutions than in acid solutions. I n noting the relative order of effectiveness of a variety of amino acids as inhibitors in the Raschig synthesis, the simple ones, such as glycine, alanine, valine, and leucine, exhibit copper complexing action. This action is not very profound if the effectiveness of these substances on an equal weight basis in alka-
I
I
I
0.2 0.4 0.6 0.8 G R A M S PER 200 ML.SOLN.
A. B. C.
D.
E.
Sea Kern-Type Sea Kern-Type Sea Kern-Type Sea Kem-Type 6ea Kern-Type
1 5
6 8 9
F. Superloid U . Kelmsr H. Kelgin I. Gelatin
This same concept of multiplicity of coordination sites appears to be operative when histidine, containing the imidazole nucleus linked to the terminal methyl group in alanine, is used as a complexing agent. Neither of the parent compounds is as effective as histidine in complexing copper. It is conceivable that in alkaline solution a tri- or possibly a quadridentate structure characterizes the metal ion-histidine complex. Asterisks in the structural formulas indicate possible sites for attachment of copper either by replacement of an acidic hydrogen or by coordination. Even though histidine is remarkably effective it constitutes only a minor constituent in gelatin (
