as noted hereinbefore , x is a halogen , the halogen generally being chlorine . the value of n and n &# 39 ; generally ranges from 1 to 5 and preferably has a value of 2 . both r and r &# 39 ; can be the same or different alkyl groups and each alkyl group contains from 1 to 4 carbon atoms , and each preferably contains from 1 to 2 carbon atoms . the preferred compounds of this invention are bis 2 , 4 - dichlorophenoxyacetate and bis 2 , 4 - dichlorophenoxypropionate . the compounds of this invention are water - insoluble and are therefore capable of removing themselves from soil and water by means of decomposition due to soil bacteria and have been found to be non - toxic to aquatic life and small animals , yet the compounds can be made water - miscible , if so desired . some of the plants controlled by the novel compounds of this invention include , for example , hydrilla , coontail , watermillfoil , pondweed , stinkweed , naiad , bullrush , chickweed , cockleburr , duckweed , elderberry , morning glory , mustard , waterlilly , dogfennel , pigweed and many other common weeds . the novel compounds can be prepared by using compound ( a ) as a reactant or by initially forming said compound ( a ) by the reaction of two moles of a halogenated , preferably chlorinated , phenoxyalkanoic acid with an equimolar amount of an aqueous solution of an alkali metal or ammonium hydroxide which is heated to a temperature sufficient to cause said halogenated phenoxyalkanoic acid to become solubilized therein just prior to the addition of said acid . the resulting reaction product which is present in solution contains a compound corresponding to compound ( a ), above , said compound then being reacted with an aqueous solution of 1 mole of a compound ( b ) wherein m is ammonium or an alkali metal , said alkali metal generally being sodium or potassium . compound ( b ) is preferably ammonium persulfate and is preferably present in 1 , 000 ml . of water when combined with compound ( a ) to form the novel compounds of this invention . in accordance with a preferred embodiment of this invention , 2 moles of 2 , 4 - dichlorophenoxyacetic acid is initially added to a heated aqueous solution of potassium hydroxide ( wherein 2 moles of potassium hydroxide is present in 1 , 000 ml . of water ). the aqueous solution of potassium hydroxide is then heated to a temperature sufficient to cause said 2 , 4 - dichlorophenoxyacetic acid to become soluble in said water which is generally achieved at temperatures up to about 95 ° c . a clear light brown solution results and 1 mole of ammonium persulfate in 1 , 000 ml . of water is then preferably added to the light brown solution resulting in the formation of a light tan precipitate that is recovered by filtration and suction . the tan precipitate , bis 2 , 4 - dichlorophenoxyacetate , is preferably dried , under vacuum at a presaure of about 5 mm . pressure and at a temperature of between about 70 ° and 90 ° c . and preferably between 80 ° and 90 ° c . with best results at 80 ° c . the filtrate contains 1 mole of ammonium sulfate and 1 mole of potassium sulfate that can be recovered by drying and can be subsequently used as an agricultural fertilizer . in preparing the compounds of this invention , other halogenated phenoxyalkanoic acids can be substituted for the 2 , 4 - dichlorophenoxyacetic acid , including , for example , p - chlorophenoxyacetic acid , 2 , 4 , 5 - trichlorophenoxypropionic acid , 2 , 3 , 4 , 5 , 6 - pentachlorophenoxypropionic acid , 2 , 3 , 5 , 6 - tetrachlorophenoxyacetic acid , forming respectively , bis p - chlorophenoxyacetate , bis 2 , 4 , 5 - trichlorophenoxypropionate , bis 2 , 3 , 4 , 5 , 6 - pentachlorophenoxypropionate and bis 2 , 3 , 5 , 6 - tetrachlorophenoxyacetate , the compounds of the present invention can be present in combination with at least one inert carrier , said compounds preferably being present in a herbicidal amount . thus , the compounds of the present invention can be uniformly admixed with any of the well known free - flowing particulate dry inert solid carriers which may be organic or inorganic . these inert carriers include , for example , sawdust , the flour derived from soybeans , tobacco , walnut shell , wheat , wood by - products , lignin and lignocellulose , ligninsulfonic acid , cork , urea - formaldehyde , resins , silicas , carbonates , calcite , dolomite , silicates , tricalcium phosphate , boric acid , etc . the amount of active ingredient present being determined by the usefulness of the product . in addition , the compositions may optionally contain from about 0 . 5 to about 1 . 0 weight percent of a surfactant or wetting agent , which renders the products wettable and dispersable , thereby facilitating the application thereof in the field . the ingredients may be simply mixed together thoroughly with said inert carrier or blended and then passed through a high - speed grinder , after which the mixture is a free flowing product . the surfactants disclosed in bulletin e - 607 of the bureau of entomology and plant quarantine of the united states department of agriculture , or surface active agents disclosed in u . s . pat . nos . 2 , 426 , 417 ; 2 , 655 , 447 ; 2 , 412 , 510 and 2 , 139 , 276 , are suitable for use in the practice of this invention . three pounds of a composition in the form of a 325 mesh powder and containing the following ingredients : ______________________________________ by weight : ______________________________________bis 2 , 4 - dichlorophenoxyacetate 40 % surfactant ( dupanol c ) 1 % diatomaceous earth ( attaclay ) 59 % ______________________________________ was added to 100 gallons of water . this aqueous composition will control the following weeds present with sugarcane : spiny amaranth , carpetweed , geranium , cressleafed groundsel , common lambsquarter , mexicantea , pellitoryweed , common purslane , ragweed , sowthistel and toadflax . field corn was planted in 3 foot square flats wherein the seeds were equally spaced at 4 inch intervals . after planting , the surface of each flat was dusted with 9 . 4 gms . of a powder composition containing the following : ______________________________________ by weight : ______________________________________bis 2 , 4 - dichlorophenoxyacetate 10 % surfactant ( dupanol c ) 1 % diatomaceous earth ( attaclay ) 89 %. ______________________________________ the ingredients were initially mixed in a ribbon type blender and are thereafter passed through a high speed grinder to form a smooth , 325 mesh powder . the corn germination was ninety - two percent on three replicated flats while there were no broad leaf weeds observed in the flats . thirty pounds of bis 2 , 4 - dichlorophenoxyacetate was dusted on one acre of a canal heavily infested with underwater growth . hydrilla , coontail , watermillfoil , waterlilly , pondweed and naiad were each observed as being successfully controlled at the end of a three - week period . no ill effect upon aquatic life was observed . a liquid composition was prepared by dissolving 2 , 722 gms ., of bis 2 , 4 - dichlorophenoxyacetate in 1 , 000 gms . of a 50 percent solution of ethylenediamine in water . forty grams of surfactant , amine salt of a higher secondary alkyl sulfate , was added thereto , with agitation . water was added to make one gallon . one quart of this composition , when added to 100 gallons of water and sprayed upon an acre of uncultivated raw land , controls the following weeds ; bindweed , bullthistle , chickweed , cockleburr , dogfennel , duckweed , elderberry , morning glory , mustard , pigweed , purslane , sowthistle , spiny amaranth , stinkweed , thistles , virginia creeper and wild garlic . two moles of 2 , 4 - dichlorophenoxyacetic acid were dissolved in 1 , 000 ml . of water containing 2 moles of potassium hydroxide . one mole of ammonium persulfate was then dissolved in another 1 , 000 ml . of water and then the 2 aqueous solutions were admixed with each other . instead of filtering the precipitated bis 2 , 4 - dichlorophenoxyacetate , the total reaction product was vacuum dried within the temperature range of 70 ° to 90 ° c . and at about 5 mm . hg . of pressure . the yield was 725 gms . which is 97 % of the theoretical yield . the anhydrous product produced consists of bis 2 , 4 - dichlorophenoxyacetate , ammonium sulfate and potassium sulfate , said homogenous mixture thereafter being passed through a high speed grinder to produce a free flowing powder . the homogenous mixture as prepared in example five is added to 6 , 525 gms . of talc and ground in a ball mill for eight hours resulting in the formation of a fine free flowing powder . this powder was used to cover the surface of the furrow when corn was being cultivated . the powder covered about an acre and a half . unexpectedly , the weeds in this treated area were controlled and the small amount of fertilizer was beneficial to the corn .
compounds useful as plant growth regulators having the formula : ## str1 ## wherein x and x &# 39 ; are each halogens , r and r &# 39 ; are each alkyl groups containing from 1 to 4 carbon atoms and n and n &# 39 ; each have a value from 1 to 5 . method of preparing said compounds is also disclosed .