Patented May 10, 1938, 2,117,158

UNITED STATES PATENT OFFICE

2,117,158 ' ' METHOD OF EXTERMINATING-CORN > BEETLES AND OTHER VEBMIN ' Werner Freyberg and Walter Haupt, Delitzsch/ Sachsen, Germany, assignors to Ernst Freyberg Chemische ‘ Fabrlk Delltia, Delituch/Sachsen, Germany v No Drawing. Application October 16,1935, se; $314 No. 45,368. In .Germany November 6, .7 Claims. ‘(Cl- .. 99—225) This invention relates to the extermination of never gas-tight cannot be ?lled with large quanti corn beetles and other vermin.- . ties of' phosphine since, apart from the large The damage caused by the corn beetle to grain quantity of phosphine which would be necessary. stored in the granary is only too well-known to the danger associated with its use would exclude 5 the persons concerned. The annual value of the the practical employment of such a process. grain which is destroyed by com beetles is It has now been unexpectedly found that the estimated to amount to about 100,000,000 reichs development of phosphine in a concentration mark for Germany alone. In spite of the extreme which is fatal to corn beetles and other vermin importance of the problem of exterminating corn can-be successfully obtained by placing solid sub 10 beetles and like vermin, no one has yet suc stances which evolve phosphine in theimmediate 10 ceeded in discovering an absolutely reliable neighbourhood of the grain, that is between or means for eradicating these and other pests from close beside or cum in the heaps of grain which grain-and other seeds. Sprays must, of course, are attacked by the corn‘beetles. ‘ be excluded from the start for this purpose as'the ‘ As the, solid substances which develop phos-- V 15 grain stored in the granary would be much phine, all._possible phosphides, such as calcium 15 damaged if these were used. Gassing the phosphide, barium phosphide, aluminimn phosa granaries with poisonous gases appeared to offer phide, magnesium phosphide and so forth are ' the greatest prospects of success but the note- I suitable for being used. These substances when worthy fact was discovered that the corn beetle they are introduced in 'a suitable packing into has a relatively high power .of resistance even to the stored grain gradually give .03 phosphine in O hydrocyanic acid, so that even this extremely continuously increasing amount owing to the poisonous gas, theme of which moreover is‘ asso moisture contained in the grain. The evolution ciated with much inconvenience and danger, can~ of gas is still further promoted owing to the fact not be said to be absolutely certain in its action. ‘ that grain which has been attacked by com 25 Thus, forv example, it is stated in a lea?et of "the beetles generally contains a higher percentage of Biologische Reichsanstalt of Berlin-Dahlem is moisture and is also of a slightly higher tem sued in June 1934, that “Absolutely reliable and perature'than sound grain. It is particularly im thoroughly e?ective‘ gassing means for checking ' portant that the phosphine should'be evolved the corn beetle have not yet been found up to the. gradually when the new process is employed. 30 present time.” I . On the one hand, the danger of self-ignition It is therefore an‘ object of the present inven— which might be present if a large quantity of ‘ tion to provide new methods of exterminating phosphine were suddenly evolved is obviated with corn beetles and other vermin in grain. certainty. On the other hand, it is just this slow It is another object of the invention to pro- " action of a, gradually increasing concentration of 35 vide a method for eradicating corn beetles and poisonous gas which appears to effect the killing other harmful vermin, 'as- well as their‘larva'e, of the corn beetles with absolute certainty, where from stored grain and other seeds. as the sudden action of large quantities ofthe It is a further object of the present invention poisonous gas appears to put the vermin into a to provide methods of ‘developing phosphine in state in which they are insensitive ‘to further 40 granaries in concentrations su?lcient to kill corn quantities of the‘ gas, without, however, being 40 beetles and their larvae. ' completely killed. 7 ' It is also an object of the-invention to provide’ In order to prevent as far as possible the escape methods of [evolving phosphine from calcium of the poisonous gas into the neighbouring atmos phosphide and other similar phosphides without phere and to ensure a gradual increase of the I 45 danger of self-ignition. \ concentration of the gas in the heaps of grain It is ?nally an object of the present invention which are attacked by the vermin, it is advisable to provide a method for gassing stored grain to cover the grain with sacks, tarpaulins, paper without using gas tight chambers. or the like during the treatment. ' Other objects and advantages of the invention It has been found that with this treatment will appear from the following description. the corn beetles and other harmfulinsects, as so The poisonous action of phosphine on corn well as their'larvae, which may be contained in beetles and other vermin is in itself well known, the grain are killed, although, if the dosage of ' , Nevertheless, it has not previously been possible the compound which evolves the phosphine be in practice to use this gas in granaries and the correct, afterri to 8 days hardly any smell of like. Naturally, granaries which are practically phosphine can be noticed in the granary, so that 2 2,117,15e the granary can then be entered as usual without of phosphine which may still be adhering to the danger and the residue of the vermin exterminat grain. ing agent can then be removed from the grain. As has already been mentioned, the most var The dead corn beetles and other insects can be ied phosphides such as calcium phosphide, bar separated from the grain in known manner, for ium phosphide, aluminium phosphide, magnesium example by winnowing whereby the grain simul phosphide and the like can be employed. The taneously becomes aerated‘ and the last traces most practicableform in which to use the phos of any odour of phosphine which may adhere phide is, of course, in the form of powder. A vto it are eliminated. ( powder can not only be easily measured out with a - vIn order to introduce into the heap of grain measuring vessel, spoon or ?lling machine but 10 the compound which evolves phosphine, the com the properties of a substance are also most uni pound must be packed in a suitable gas-pervious form when it is in powder form. It has been packing. It has been found advantageous for found,- however, that the pulverulent phosphide this purpose to wrap the phosphide in a dry bag compounds of' calcium, magnesium and barium made of paper, fabric or metal gauze which itself . are not very stable. They give oil? hydrogen 15 is contained .in a case which is made of ‘sheet phosphide in the sheet metal boxes which are metal, arti?cial material, porcelain or the like employed for their carriage or transport and may and is perforated and is again inserted in a sec thereby burst open the boxes. It has also been ond bag made of gauze.’ This packing is pref found by experience that phosphides in the form 20 erably provided with a thread to which a coloured of lumps or pieces keep better, so that they can 20 tab is attached so as to enable the bag to be easily be placed on the market in tightly closed sheet found in the heap of grain after the gassing has metal containers. , been completed. . _ g I Calcium phosphide in the form of lumps or -When used'in practice thenew process is ex pieces, however has the disadvantage that it can 25 tremely inexpensive. Thus, under. favourable only be measured out into the form of doses with 25 conditions, it has been‘ found by experience that di?iculty. Pulverization by the user in a mor it is su?icient to .use about 30 grammes -of cal tar or the like‘ before use is out of the question cium phosphidevto each cubic metre, i. e. about because the pieces of calcium phosphide are very 15 hundredweight, ofigrain. ‘Under less favour 'hard. A further undesirable property of cal 30 able conditions, for example, when thetempera cium phosphide is that thecontent of phosphide 30 ture is lower, several times the amount indicated in the individual pieces varies. may, however, be employed. In' order that When gasifying the phosphides of calcium, quantities of the material which always evolve magnesium and, barium in the form of lumps, it the same amount of poisonous gas may always has been found thatvthe products of decomposi 35 be available, it is advisable to employ the calcium tion formed during the gasi?cation occupy a con phosphide in the form of tablets of standard side. siderably greater volume in comparison with the The new process has the great advantage that, ' original \material and this increase in volume in contradistinction to 'all the gassing processes may amount to up‘to about 30%. Consequently hitherto known, it is not necessary to employ gas the sheet metal containers which, for- example, tight chambers,- yet the vermin including their may be employed for the gassing may in some 40 larvae are destroyed with-absolute certainty. At cases be burst open so that the poisonous mate the same time, it has unexpectedly been found rial may escape. None of these disadvantages that the grain itself is not attacked. The grain however is possessed ‘by aluminium phosphide not only remains palatable but also loses the which is therefore particularly suitable for use 45 odour of phosphine with surprising rapidity.> in exterminating vermin especially in small works 45 With thenew process also, no residue whatever and when used by laymen. V' remains behind in the grain so that the treated Aluminium phosphide is a brittle,.powdery, grain can be employed without objection as food sometimes slag-like, porous.mass which can be for human beings and animals just as fresh grain. uniformly disintegrated very easily with little The use of the new process necessitates no spe pressure and without any strong evolution of 50 cial technical knowledge whatever so that the phosphine'taking place. Aluminium phosphide new vermin extemiinating process can be car therefore can very easily be made up into doses. ried out without employing technical oper The preparation can be mixed well so that a .. ators, as was necessary when carrying out other; uniform content of'phosphide can be guaranteed. 55 known processes, the more so because phosphine The most important ' advantage of aluminium 55 always gives a warning of its presence owingto phosphide over the phosphides of calcium, mag its characteristic odour. _ ' nesium and barium is, however, the excellent sta Example.-—The grain is shovelled into heaps bility of the powdered aluminium‘ phosphide in of about 1/2 metre in height. The calcium phos-s sheet metal containers. When ?lled into boxes 60 phide contained in its packing is‘ inserted at a it still remains undecomposed. With powdered 60 depth of about 25 centimetres into the heaps of aluminium phosphide, the highly dangerous and .grain. In order to obtain a rapid and uniform therefore much feared development of phosphine permeation of the heap of grain by the phosphine, does [not take place during the time when it is the use of several gassing containers at suitable stored in the boxes. ' - - distances apart within the heap of grain is ad In comparison with the other phosphides, alu 65 visable. After the introduction of the contain minium phosphide reacts somewhat more slowly ers. the heaps of grain are covered with a tar , with water or with moisture in the air. Nevere \ paulin. After eight days, the covering is re theless it can be decomposed’ completely and to moved and the containers are taken away. The such an extent that the residue is no longer poi grain is then preferably subjected to a winnow sonous. The volume of the residual products is 70 ing treatment in ‘order to remove the dead ver only about 15% greater than that of the unde min, such ascorn beetles, meal beetles, meal ‘ composed substance. The increase in volume is ‘ moths, grain capuchins, chapra beetles, maize therefore only about half that which occurs in beetles, rice beetles, larder beetles and other in- the case of the phosphides of calcium, magnesium 7-5 sects, fand to eliminate the last traces of any odour and barium. Bursting of the gassing containers 75 8,117,168 3. has therefore not been observed with aluminium commercial product has a phosphide content 01’ phosphide. . 90% and more. , The phosphide preparations from calcium. 5. It is not liable‘to catch fire because in the magnesium and barium moreover always contain presence of moisture only gaseous PH: is formed only about 30% pure phosphide and at the most and no formation of self-ignitible hydrogen phos 5 60% as production in a concentrated form gives phide occurs. - ' rise to considerable technical diiilculties. Alumin ‘6. When decomposed by moisture there is only ium phosphide, on the other hand, can be manu a small increase in volume which is not su?icient Iactured in a high degree of purity and with a to burst the gassing container. , 10 phosphide content of about 90 to 98% without '7. The residual products from the decomposi 10 any special diillculty. tion are practically non-poisonous. .As it is desirable in many cases that the phos Having now particularly described and ascer- . phine produced should be easily detected by any tained- the nature of our said invention and in body even when highly diluted, when manufac what manner the same is to be performed, we turing the aluminium phosphide it is easily pos declare that what we claim is: I ' 16 sible by the addition of sulphur to e?ect the for 1. The method of exterminating vermin and mation of aluminium sulphide which decomposes their larvae in grain consisting in packing a metal in a similar manner to aluminium phosphide with phosphide in a gas-perviouspacking and insert evolution of the pungent hydrogen sulphide. As ing the said packing without addition of a re 20 is well-known. the odour oi’ hydrogen sulphide agent into a heap of grain. 20 can be detected considerably more easily than 2. The method of killing corn beetles and their that of phosphine, so those who are unaware can larvae in grain consisting in wrapping a metal be warned by it in good time 0! the presence 01' phosphide in a gas-pervious packing, introduc the phosphine. _ ' ing the wrapped phosphide into a heap of grain, 25 An addition of sulphur to a ?nished phosphide covering the grain and allowing the phosphine 25 has previously been proposed. This addition, (PHa) formed in the grain by the reaction of the however, was only for the purpose of forming an moisture contained in the grain and the atmos incrustation on the individual pieces of phos phere with the said metal phosphide to act on phide in order to obtain thereby certain advan .the grain for several days. . 30 tages over the usual phosphide pieces or lumps, 3; The method according to claim 2 in which 30 which advantages, however, are present from the calcium phosphide is used as a metal phosphide. beginning when aluminium phosphide is used, 4. The method according to claim 2 in which namely, stability in air, impossibility of self-ig aluminium phosphide is used as‘ a metal phos nition, granulation oi the ‘productand so forth. phide. It was not. however, recognized that the forma— ‘5. The method according to claim 2 in which 35 tion of hydrogen sulphide on the decomposition aluminium phosphide containing aluminium sul of the sulphide by moisture in the air would give phide is used as a metal phosphide. ' an excellent warning of the presence of phosphine 6. The method of exterminating vermin and which is far less easily perceptible. Since hydro their larvae in grain consisting in packing a metal gen sulphide has almost the same specific gravity, phosphide in a gas-pervious packing, inserting 40 as phosphine, the hydrogen sulphide will be simi the said packing without addition of a reagent larly distributed in the atmosphere permeated by into ‘a heap of grain, covering the grain, taking the phosphine. . away the gas-pervious packing with its contents ' In accordance with the invention, the sulphur after several days andsubjecting the grain to a 45 is added to the aluminium phosphorous mixture winnowing treatment to separate the grain from before the manufacture. Particular importance dead vermin. is attached to the aluminium sulphide being uni '7. The method of freeing grain from corn bee formly distributed in the aluminium phosphide. tles, their eggs, larvae, and other vermin, com Aluminium phosphide therefore‘ has the fol prising wrapping aluminium phosphide in a gas 50 pervious packing, inserting such packing without 50 lowing advantage over the phosphides of calcium, addition of a reagent into a mass of grain, per magnesium and barium: mitting the phosphine (PI-I3) ‘evolved from the 1. It can be easily converted into powder form phosphide by the reaction of the latter with the and can therefore easily be dispensed in doses. moisture contained in the grain and the atmos 2. It can be packed and transported easily phere to act on the grain for several days, tak and without danger. - ‘ vlng away such packing and removing the dead 3. It can easily be delivered with a uniform vermin from the grain. phosphide content. WERNER FREYBERG. 4. It is oi’ the highest quality, since even the WALTER HAUPT.