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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 18, No. 6
The Fluosilicates as Insecticidesli* By S. Marcovitch AGRICULTURAL EXPERIMENT STATION, KNOXVILLE, TENN.
HE first extensive experiments with the fluosilicates by the commercial sodium fluosilicate to soy bean foliage or as insecticides were carried out a t Knoxville, Tenn., alfalfa when diluted with an equal quantity of hydrated lime. in the spring of 1924. Comparatively favorable The control of the striped cucumber beetle has previously results were obtained which were reported in Bulletin 131 been far from perfect. It is a very difficult insect to poison of this station. The sodium salt was the only one available with arsenicals because they act as repellents. Since the in commercial quantities, but it was not particularly adapted beetle has the habit of cleaning its feet by drawing them for dusting. Last summer one concern placed a “light” through its mouth, it would be expected to yield to the and “extra light” sodium fluosilicate on the market, and fluosilicates, and such was found to be the case. On June there has also appeared a commercial calcium fluosilicate. 12, several rows of cucumbers were dusted lightly with comThese chemicals were tried out in the field and much ad- mercial sodium fluosilicate about seven o’clock in the morning. ditional information y a s obtained. The results are not Eight hours later it was difficult to find a live specimen, entirely conclusive, however, because the hot, dry summer while dead beetles were numerous on the ground about the kept the bean beetles from multiplying. plants. As some foliage injury is produced when the commercial sodium fluosilicate is used undiluted, it would be Sodium Fluosilicate-“Extra Light” advisable to mix it with 2 or 3 parts of hydrated lime. The The “extra light” consists of 70 to 75 per cent sodium “extra light” sodium fluosilicate also gave good control fluosilicate. According to the distributors, the remainder and no burning when used undiluted. Cage tests showed is silica. It was found, however, to be alumina which was that the beetles succumbed to heavy applications of the used as a colloid to make a bulkier precipitate. This material calcium fluosilicate compound. occupies about 60 cubic inches to the pound and represents When the fluosilicates were mixed with bran in the proa decided improvement as far as bulk is concerned. The portion of 1 to 20, they were found effective in cage tests individual particles vary in size from 5 to 30 microns. A against grasshoppers and cutworms. There is some evidence good grade of calcium arsenate occupies 80 cubic inches to that arsenic is somewhat repellent when used in cutworm the pound and the particles appear to be 2 to 4 microns baits, but this does not appear to be the case with the fluorine in size. For many insects there appears to be sufficient compounds. fluorine in the “extra light” when used undiluted to secure Roaches were readily controlled with commercial sodium a kill. For insects that feed sparingly, such as the boll fluosilicate by sprinkling some of the powder in the corners weevil, the large amount of filler detracts seriously from the of the pantry or on kitchen floors. I n a few cases dead mice value of the material. It cannot be mixed with hydrated were found where the powder had been used. Sodium lime without seriously impairing its toxicity. When used fluosilicate is also very useful against chicken lice when undiluted the “extra light” is safer on foliage than the dusted in the feathers. commercial sodium fluosilicate. On tobacco severe injury One great advantage of the fluosilicates over the arsenicals sometimes results. is their effectiveness against a variety of insects which Calcium Fluosilicate cannot be controlled by arsenic. Furthermore, the fluoThe calcium fluosilicate was marketed as “calcium fluo- silicates appear fully as toxic as the arsenicals in quantitative silicate compound.” This material is a by-product in the tests against certain insects, whereas against man arsenic volatilization method of treating phosphate rock for phos- is far more poisonous. Sollman4 states that the fatal dose phoric acid. It is insoluble and, therefore, safe on foliage, for the trioxide varies from 0.1 to 0.3 gram. Arsenic is such as tobacco. It is light and fluffy, the particles being also a nerve and capillary poison so that minute quantities about 5 microns in size, and marketed in two forms, one are capable of destructive action. The fatal dose for sodium occupying approximately 70 cubic inches to the pound and fluosilicate is not given, but for sodium fluoride is said to the other approximately 120 cubic inches to the pound. be 0.5 gram per kilogram of body weight. This means that When used at the rate of 5 pounds per acre, the “compound” arsenic trioxide is from 100 to 300 times as poisonous to is not so toxic as the sodium fluosilicate. However, a t the higher animals as sodium fluoride. rate of 30 pounds to the acre, the control against the Mexican Compatibility with Fungicides or Insecticides bean beetle was good. The manufacturers have discovered a method of increasing Calcium fluosilicate does not appear to react to any great the fluorine content of the “compound’J which should ma- extent with lime-sulfur or Bordeaux mixture. Sodium terially enhance its value as an insecticide. fluosilicate, however, precipitates sulfur out of the limesulfur and the two are, therefore, not compatible, especially Test with the Fluosilicates against Certain Insects for use on apples. A 3:3:50 Bordeaux with sodium fluoThe “calcium fluosilicate compound” appears to be very effective against flea beetles, such as the new mint flea silicate at the rate of 2 pounds to 50 gallons of water was not beetle in Michigan. I n Arkansas, Baerg3 found that the injurious to potato foliage and was toxic to the larvae of blister beetles, heretofore not successfully controlled by the potato beetle. According to Kerr and Smith,5 sodium fluosilicate with arsenicals, are very susceptible to the fluosilicates. These beetles are especially injurious to soy beans where they either calcium arsenate or Paris green tends to liberate are found in swarms. KO appreciable injury was caused free, water-soluble arsenic (As20s) with consequent injury to foliage. I n one experiment 87.87 to 93.80 per cent of Received February 18, 1926. the total amount of As205in the calcium arsenate was leached 2 A somewhat more detailed account of the fluosilicates is to appear
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in Bulleltn 134 of the Tenneqsee Experiment Station. a Ark. Agr. Expt. Sta , Bull. 201 (1925).
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Manual of Pharmacology, 1924. The Official Record, U. S. Dept. Agriculture, December 2, 1926, p. 5
ISDUSTRIAL A N D ENGINEERING CHEMISTRY
June, 1926
out of a combination of distilled water and a mixture of equal parts of calcium arsenate and sodium fluosilicate. With lead arsenate only 1.5 per cent of the total amount of Asz05 was leached out, while Paris green gave 9.4 per cent. Sodium fluosilicate in a mixture of calcium arsenate or Paris green is, therefore, not safe to foliage. Calcium arsenate left in dust guns may also be responsible for foliage injury when the same gun is used for dusting with sodium fluosilicate. Germicidal Value
In a paper presented before the American Phytopathological Society on December 31, 1925, H. W. Anderson
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discussed “The Control of Bacterial Spot of Peach with Sodium Silicofluoride.” Bacterial spot (Bacterium pruni), considered the most serious disease of the peach in Illinois, is not controlled by the ordinary fungicides. Dr. Anderson found that sodium silicofluoride in dilutions of 1 to 4000 to 1 to 4500 would always render both sterile when inoculated with Bacterium pruni. Sodium silicofluoride was found only moderately fungicidal, inhibiting the germination of bitter rot spores (Glomerella cingulcsta) in dilutions of 1 to 800 when added directly to the spores suspension. Field tests showed practically no infection of bacterial spot, whereas those trees not sprayed with sodium silicofluoride showed 20 to 80 per cent of the leaves infected.
The Determination of Fluorine‘ By F. G. Hawley ISTBRNAIIOSAL SMELTING Co., INSPIRATION, ARIZ
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HE difficulties attending the quantitative determina- weighed as such, has several advantages, the principal ones tion of fluorine in ores or minerals containing con- being the granular nature of the precipitate, which permits siderable amounts of other elements are quite gen- easy filtering. and the fact that under the conditions of the erally recognized. By using long and laborious methods and assay lead chlorofluoride is somewhat more insoluble than taking special precautions fairly accurate results may fre- calcium fluoride. A serious objection is that several other quently be obtained, but in general the method- in use are acid radicals, such as sulfates, phosphates, arsenates, etc., far from satisfactory. would, if present, also form insoluble lead salts and be weighed The two methods most frequently used are the Berzelius- with the lead chlorofluoride. The procedure as published is Rose method, in which the fluorine is precipitated and weighed only applicable to soluble fluorides and therefore is of very as calcium fluoride, and the volumetric method of Offerman, limited application. A method has been dewherein the fluorine is volavised which is free from the tilized as silicon tetrafluo- h ,( ride, which is received in foregoing objections, a n d A short rdsume‘ is given of some of the difficulties water and the hydrofluosiseems equally well adapted usually encountered when determining fluorine by the licic acid formed is titrated to simple fluorides, as fluormethods commonly used. A new method is described with alkali. spar, and to more complex in which fluorine is determined indirectly. It is first The Berzelius-Rose minerals, such as topaz or precipitated as lead chlorofluoride, and after filtering the micas. It can be used method is probably used from the solution this is decomposed and the amount more commonly than that successfully in presence of of chlorine present determined, and from it the amount fairly large amounts of most of O f f e r n i a n and in the of fluorine is calculated. The method is especially of the other elements. The hands of an expert will genrecommended for low- to medium-grade ores, on which erally yield results that are accuracy obtainable, espeit gives excellent results. On high-grade material the fairly accurate, but most cially on low-grade and imresults are not quite so accurate. chemists usually get low repure material, is somewhat Experimental data are given showing the degree of sults. An objection to this greater than that usually accuracy that may be attained under different condimethod is the necessity of obtained by the Berzeliustions with pure material, and also that possible in removing all silica, which Rose method. Small presence of various other elements. r e q u i r e s t w o filtrations, amounts of sulfates and P h b s p h a t e s , if present, ]’ ‘1 phosphates have little inm u s t a l s o b e removed, fluence on the results, but The precipitated calcium fluoride is gelatinous and difficult when a large percentage is present the determination is less to filter. The presence of calcium carbonate partly remedies accurate. If either is present in notable amounts it can be rethis, but then a good separation of the fluoride from the moved by a preliminary leach with 10 per cent acetic acid.6 carbonate is rather difficult,. The Offerman method is simple Several variations of the method are given in order t o make in operation but requires considerable special and cumber- it better adapted to varied conditions. I n each, the fluorine some apparatus. For some minerals it is unreliatlle because is determined indirectly. being first precipitated as lead chloroof difficulty in completely decomposing the fluorine com- fluoride, the chlorine in this determined, and from it the pounds with sulfuric acid. Excellent critical reviews of these amount of fluorine calculated. methods, as well as some others, have been given by HilleMethod brand,*ddolph,3 and Wagner and Ross.4 A method published by Starck,j in which the fluorine is Fuse 0.5 gram of sample with 7 or 8 grams of Na2C0s precipitated as t’he double salt, lead chlorofluoride, and K2C03in a platinum crucible or dish. If the sample does not Received February 2, 1926. * “The Analysis of Silicate and Carbonate Rocks.” U . S Ceo2. S u r u e y , contain about four times as much silica as fluorine it should be added, but avoid much excess. If sulfur is present, add Bull. 700. 3 J . i l m . Chem. Soc., 37, 2500 (1913). enough ?odium peroxide to oxidize it. also avoiding much es-
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‘ THISJ O U R N A L , 9, 1116 (19171. 5
Z . anoyg. Chem., 70, 173 (1911).
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Scott, THISJounsri., 16, 703 ( 1 9 2 4 .
