INDUSTRIAL AND ENGINEERING CHEMISTRY
July 15, 1929
point in the titration was observed. The sulfur dioxide was prepared by dropping sulfuric acid on sodium sulfite. WATERVAPOR-The apparatus is designed to absorb all moisture before the sample reaches the iodine pentoxide, but for the purpose of this determination 0.1 cubic foot (2832 cc.) of nitrogen saturated with water vapor was passed directly into the iodine pentoxide. An indicated amount of 0.003 per cent carbon monoxide was obtained. No satisfactory explanation of this reaction is given a t present. FORMALDEHYDE-Formaldehyde was prepared by heating paraform tablets used for disinfecting purposes. The gas analyzed 27.3 per cent carbon dioxide, 2.8 oxygen, 6.3 hydrogen, 2.8 carbon monoxide, 51.4 aldehydes, and 9.4 inerts. The aldehydes were determined by slow combustion with oxygen. For analysis in the iodine pentoxide apparatus a sample of this gas was used after it had been passed through potassium hydroxide, fuming sulfuric acid, potassium pyrogallate, and the copper oxide furnace. A sample containing 1.0 per cent of aldehydes mixed with nitrogen gave an indication of 0.025 per cent carbon monoxide when passed through an apparatus with the chromic acid a t room temperature. Cold chromic acid apparently oxidizes aldehydes only partially. When 0.9 per cent aldehyde mixed with nitrogen was passed through the apparatus having one tower of chromic acid a t 100" C., no indication of a reaction with iodine pentoxide was obtained. This experiment would indicate that heated chromic acid oxidizes aldehydes. OXIDES OF NITRoGEN-Although there is considerable doubt as to the presence of appreciable quantities of oxides of nitrogen in the products of combustion of gas, there is of course such a possibility. Oxides of nitrogen, mainly nitric oxide and nitrogen peroxide, were prepared by the action of nitric acid on copper. Quantities varying from 0.13 per cent to 1.06 per cent oxides of nitrogen mixed with nitrogen were passed through the apparatus. I n no case was there any indication of a reaction with iodine pentoxide, nor did this amount of oxides of nitrogen affect the satisfactory titration of a known quantity of iodine.
133
Conclusions
The iodine pentoxide apparatus developed by the U. S. Bureau of Standards and the A. G. A. Testing Laboratory may be used successfully for routine analysis of carbon monoxide in concentrations as low as 0.002 per cent in the products of gaseous combustion when: (1) carbon dioxide, oxygen, hydrogen, methane, ethane, hydrogen sulfide, sulfur dioxide, nitrogen, and oxides of nitrogen are present in small quantities; (2) formaldehyde is present in less than 1 per cent if one chromic acid tower is heated to 100" C. Correct readings cannot be secured where relatively large quantities, 0.04 to 1.9 per cent, of ethylene are present in the products of combustion. Literature Cited (1) Anthes, Gas Age-Record, 56, 769 (1925). (2) Berry, Brumbaugh, Eiseman, Moulton, and Shawn, Bur. Standards, Tech. Paper am. (3) Bull. SOL.chim., 17, 256 (1915). (4) Burrell, Seibert, and Jones, Bur. Mines, Bull. 197, p. 63. (5) Compt. rend., 147, 1306 (1908). (6) Davies and Hartley, Gas J . , 174, 530 (1926). (7) Davies and Hartley, Ibid., 179, 334 (1927). ( 8 ) De la Hade and Reverdin, Chem.-Ztg., la, 1726 (1888). (9) Ditte, Bull. SOC. chim., 13, 318 (1870). LO) Froeboese, 2. anal. Chem., 64, 1 (1915). 11) Gautier, J . Gas Lighting, 121, 547 (1890). 12) Goutal, Ann. chim. anal. chim. aggl., 16, 1. 13) Graham and Winnill, J . Chem. SOC.,105, 1996 (1914). 14) Guichard, Compt. rend., 148, 923 (1909). 15) Kattwinkel, Brennstof-Chem., 4, 104 (1923). (16) Kinnicutt and Sanford, J. A m . Chem. SOC.,22, 14 (1900). (17) Lamb, Bray, and Gildard, Ibid., 42, 1636 (1920). (18) Morgan and McWhorter, Ibid., 29, 1589 (1907). (19) Nicloux, Comgt. rend., 126, 746 (1898). (20) Seidell, J. IND.END.CAEM.,6, 321 (1914). (21) Sinnatt and Cramer, Gas World, 60, 602 (1914). (22) Sinnatt and Slater, Fuel, 2, 241 (1923). (23) Teague, J. IND.ENG.CAEM.,12, 964 (1920). (24) Weiskopf, J . Chem. Met. Mining SOL.S. Africa, 9, 258, 306 (1909). (25) Wood and Howarth, Gas J . , 175, 787 (1926). (26) Wood and Howarth, Ibid., 178, 824 (1927). (27) Wood and Howarth, 19th Rept., Gas Investigation Committee, Institute of Gas Engineers.
Analysis of Insecticides Containing Fluorine Compounds' Leslie Hart FOOD, DRUG,AND INSECTICIDE ADMINISTRATION, U.S. DEPARTMENT OF AGRICULTURE,CHICAGO, ILL.
Methods are described for the analysis of preparations HE use of fluorine comMethod for Preparations containing (a) alkali silicofluorides and boric acid ; Containing Alkali silicapounds in insecticides is increasing. Several (6) fluorides with arsenic trioxide or soluble arsenic fluorides and Boric Acid compounds; (c) fluorides, bifiuorides, and silicayears ago the only fluorine The determination of these fluorides. compound finding use as an compounds in the presence of Tables are given showing the accuracy of results insecticide was sodium fluoreach other is based on the fact obtained by these methods. ide or mixtures of it, w i t h ( 4 ) * that the silicofluoride is pyrethrum powder or borax, in roach and lice powders. Fluorides and silicofluorides,often removed from the field of reaction by precipitation as the mixed with other active insecticidal substances, are now much potassium salt in the presence of alcohol (1:2). After preused as dusts, dips, or sprays against a great variety of pests. cipitation of the silicofluoride, but without filtering, the boric The determination of fluorine is therefore of considerable acid remaining in solution may be titrated in the usual way, importance in the evaluation of these insecticide preparations. with standard alkali solution, in the presence of glycerol (6). The following methods to determine fluorine in the presence A determination of total acidity is made and the amount of of substances in which the usual methods are not applicable alkali silicofluoride is obtained by difference between the total have been developed. If the fluorine compound present is acid titration and the boric acid titration as follows: TOTAL AcmTY-Dissolve a weighed sample containing not already water-soluble, preliminary fusion with sodium about 0.4 gram total boric acid and sodium silicofluoride in carbonate is necessary.
T
1
Received February 28, 1929.
* Italic numbers in parenthesis refer to literature cited at end of article.
ANALYTICAL EDITION
134
40 to 50 cc. of water in a 200-cc. Erlenmeyer flask. Heat to boiling, add a few drops of phenolphthalein, and run in 0.2 N sodium hydroxide solution to a permanent pink. Cool, add 30 cc. of glycerol, and complete the titration with sodium hydroxide solution. After a light pink color is obtained, add 10 cc. more of glycerol and, if the color fades; continue the addition of sodium hydroxide solution to a permanent pink. Make a blank determination on the reagents used and deduct from the figure obtained for the titration. BORICACID-Dissolve a weighed p o r t i o n of sample (containing 0.1 to 0.2 gram of boric acid) in as small a volume of water as possible (not over 25 cc.) in a 200-cc. Erlenmeyer flask. Dissolve 1gram of solid potassium chloride in the mixture, and add twice as much alcohol, by volume, as there is water present. Add 30 cc. of glycerol, cool to about 5” C., add a few drops of phenolphthalein, and titrate with 0.2 N sodium hydroxide solution to a pink color remaining for at least 20 o r 30 seconds. ( T h e color gradually fades, owing t o hydrolysis of the potassium silicofluoride present, but after the first indication of the end point, two or three additional drops of 0.2 N sodium hydroxide solution will usually give a color remaining Apparatus for Determination for 30 seconds.) A blank deof Arsenic termination should be run on the reagents. The equivalent of 1 cc. 0.2 N sodium hydroxide solution is 0.01237 gram boric acid. SILrcomuoRIDE-The result obtained by titration with 0.2 N sodium hydroxide solution represents the total acidity of the sample. From this figure deduct the number of cubic centimeters equivalent to the boric acid content as obtained by the determination already described. The difference is the quantity of 0.2 N sodium hydroxide solution equivalent to the sodium silicofluoride present: l cc. 0.2 N sodium hydroxide is equivalent to 0.00940 gram sodium silicofluoride. The sodium hydroxide solution used for titration of silicofluorides should be free from silica and carbonates (1). It may be prepared as follows: Place several small clean pieces of metallic sodium in a platinum Gooch crucible, supported by a nichrome or platinum triangle over an 800-cc. paraffinlined beaker half filled with recently boiled and cooled distilled water. Cover with a bell jar, connect to a vacuum pump, and evacuate. The sodium will react slowly with the water vapor and the resulting hydroxide solution will be caught in the beaker of water. Adjust this solution to 0.2 N and keep in a bottle lined with ceresin or paraffin. Table I-Quantities
of Boric Acid and Silicofluoride Found SILICOFLUORIDE
BORICACID
Gram 0.1434 0.1250 0.1000 0.1500 0.1875 0,2500
0.2000
Gram 0.1435 0.1254 0.09Sl 0.1624 0.1869 0.2503 0.199s
I
Gram 0.2126 0.1250 0.1000 0.0500 0.0625
0.2000 0.2466
Gram 0.2120 0.1248 0,0999 0,0506 0.0621 0.1996 0.2480
Vol. 1, No. 3
Method for Preparations Containing Water-Soluble Fluorides and Arsenic Trioxide or Soluble Arsenicals
In this mixture the arsenate may be precipitated from solution as silver arsenate, while silver fluoride, being soluble, remains in solution. After filtration the arsenic and fluorine may be determined in the precipitate and filtrate, respectively, according to the usual methods. Transfer 2 grams of the sample to a 300-cc. volumetric flask. Add about 100 cc. of water. If sufficient carbonates are not present in the sample, add enough sodium carbonate to insure solution of any arsenic trioxide present. Avoid much excess. Add 50 cc. of 3 per cent hydrogen peroxide to oxidize arsenites to arsenates, and heat on the steam bath for 20 to 30 minutes. Add 10 cc. of a buffer solution which is half-molar with respect to both acetic acid and sodium acetate and a slight excess of 10 per cent silver nitrate solution. Note-The acetic acid buffer solution is used because of the solubility of silver arsenate in dilute nitric acid since nitric acid is liberated according to the reaction: NazHAsOd 4- 3AgNOs = AgsAsOc
+ 2NaNOa + HNOi
This precipitates silver carbonate and arsenate, leaving the fluorides in solution. Cool, dilute to mark, and shake thoroughly. Allow precipitate to settle, then filter through a dry filter, rejecting the first 10 to 15 cc. of filtrate. Save the precipitate for the determination of arsenic, as described later. Transfer 200 cc. of the filtrate to a 300-cc. volumetric flask, and precipitate the excess silver nitrate by adding sodium chloride solution. Cool, dilute to mark, shake thoroughly, and allow the precipitate to settle. Transfer 200 cc. of this solution to a 400-cc. beaker, after filtering as previously directed. Use this for the determination of fluorine. FLUORIKE @)-Add 2 cc. of 10 per cent sodium carbonate solution, heat to boiling, and add slowly an excess of 10 per cent calcium chloride solution. Allow the precipitate to settle, filter, and wash once with a few cubic centimeters of hot water. Dry the precipitate and filter paper in a silica dish and ignite a t a dull red heat. (A better ignition may be obtained if the precipitate is separated from the filter and the filter burned separately.) After cooling add 20 cc. of 20 per cent acetic acid and evaporate to dryness on the steam bath. Repeat the process, breaking up any lumps with a glass pestle. Take up the residue with a little hot water to which 2 to 3 cc. of the 20 per cent acetic acid has been added, filter, and wash with small portions of hot water. The residue is dried and ignited as before and weighed. The result obtained may be confirmed by fuming with sulfuric acid, which converts the calcium fluoride to calcium sulfate. Heat the fumed residue with a little ammonium carbonate, ignite, and weigh as calcium sulfate. Factors: CaF;--NaF, 1.0759. CaSOn-CaFz, 0.5735 The final aliquot of 200 cc. represents four-ninths of the original sample. FLUORINE-The results for fluorine will be slightly low because of the solubility of calcium fluoride in water and dilute acetic acid. ARSENIC-wash the precipitate of silver carbonate and arsenate obtained by the action of silver nitrate by decanting once or twice with water. Filter and transfer precipitate and filter paper to a 500-cc. distilling flask. Determine arsenic according to the method given in “Methods of Analysis, A. 0. A. C.,” 2nd edition, page 49, method 2. Add 50 cc. of hydrazine sulfate reagent, using apparatus as shown in diagram. (Hydrazine sulfate reagent consists of 20 grams each of hydrazine sulfate and sodium bromide and 400 cc. of concentrated hydrochloric acid, diluted to 1 liter.) Close the flask with a stopper carrying a 125-cc. funnel tube, and connect the flask to a condenser. Boil for 2 or 3 minutes, add 100 cc. of strong hydrochloric acid by means of the funnel
.
INDUSTRIAL AND ENGINEERING CHEMISTRY
,July 15, 1929
tube and distil until the volume in the distilling flask is reduced to about 40 cc., add 50 cc. more of strong hydrochloric acid and again distil until the volume in the distilling flask is reduced to 40 cc. Wash down the condenser, transfer the contents of the receiving flasks to a liter volumetric flask, dilute t o volume, and mix thoroughly. Pipet a 200-cc. aliquot of this solution into a 500-cc. Erlenmeyer flask, almost neutralize with 50 per cent sodium hydroxide solution, complete the neutralization with sodium bicarbonate, and add about 5 grams excess. Titrate with 0.05 N iodine solution, using starch solution as indicator. Add the iodine solution slowly until a permanent blue color is obtained. The equivalent of 1 cc. of 0.05 N iodine is 0.002874 gram arsenic oxide. The arsenic may also be titrated with 0.05 N bromate solution according to method given on page 47 of “Methods of Analysis, A. 0. A. C.”
135
reserved for total fluorine estimation. Dilute to 100 cc. with water, add about 0.1 gram of sodium carbonate, heat to boiling, and determine the fluorine as described in the section on mixtures of water-soluble fluorides and arsenic trioxide. Calculate to fluorine, deduct the fluorine equivalent of the bifluorides and silicofluorides present, and calculate the remaining fluorine to sodium fluoride. I n a private communication the author has been informed by C. M. Smith, of Insecticide Control, Food, Drug, and Insecticide Administration, that the method for bifluoride and silicofluoride is unsatisfactory when bifluoride and silica are present together, owing to the reaction between the two to form silicofluoride. These would probably be present in a mixture of commercial sodium bifluoride and commercial sodium fluoride. Results
Table 11-Quantities of Arsenic Trioxide and Sodium Fluoride Found i n Prepared Mixtures ARSENIC TRIOXIDE
Gram 0.4000 0.2000 0.2000 0.1000
Cram 0.4006 0.2000 0.1994 0,0996
SODIUMFLUORIDE
Gram 0.2000 0,2000 0.1000 0.1000
Gram 0.1982 0.1988 0,0989 0.0984
Method for Determination of Sodium Fluoride, Sodium Bifluoride, and Sodium Silicofluoride
Sodium bifluoride and sodium silicofluoride, being acid in reaction, may be titrated with standard carbonate- and silicafree sodium hydroxide solution (2,s). This titration converts both compounds into sodium fluoride, according to the equations: NaHFs NaOH = 2NaF f Hz0 NazSiFe 4NaOH = 6NaF 4-Si(0H)d TOTAL AcIDITY-Dissohe 0.5 to 1 gram of the sample in 25 cc. of cold water in a 100-cc. platinum dish. Titrate with 0.2 N or 0.1 N carbonate- and silica-free sodium hydroxide solution, using phenolphthalein as an indicator and a platinum rod as a stirrer. When the pink color fades with evident sluggishness, heat to boiling and continue the titration to a permanent pink color. This titration is recorded as total acidity, due to bifluorides and silicofluorides. After the titration is complete, transfer the solution to a 200-cc. volumetric flask, dilute to mark, and reserve for determination of total fluorine. BIFLUORIDES-weigh 0.5 gram of the sample into a loo-cc. platinum dish, add 1 gram of solid potassium chloride, and dissolve in 25 cc. of water. Add an equal volume of neutral alcohol and cool in an ice bath to as near 0” C. as possible. Titrate with 0.2 or 0.1 N carbonate- and silica-free sodium hydroxide solution, keeping the platinum dish in the ice bath, using phenolphthalein as indicator, until the red color remains for one minute. To insure accuracy, titrate slowly, so that the temperature of the mixture does not rise appreciably, and avoid excessive dilution by the standard alkali. If more than 15 cc. of standard hydroxide solution are required, repeat the titration, using either a smaller sample or stronger standard sodium hydroxide solution. This titration is calculated to sodium bifluoride. SODIUM SILICoFLuoRIDE-Deduct the equivalent quantity of sodium hydroxide solution due to bifluorides, as determined above, from the titration previously recorded as “total acidity.” The result is the quantity of standard sodium hydroxide solution equivalent to the silicofluoride present. TOTAL FLUORINE-Pipet into a 250-cc. beaker an aliquot containing the equivalent of about 0.25 gram of sodium fluoride from the 200-cc. volumetric flask containing the solution
+
+
Owing to difficulty in obtaining a pure bifluoride, mixtures containing known quantities of ingredients were not used. However, mixtures of insecticides containing these three constituents were obtained in the open market and analyzed in duplicate. The results shown in Table 111 are, therefore, probably not free from the errors indicated by Mr. Smith. Table 111-Analytical Results NaHFz NazSiFs Per cent Per cent 1 Sold as sodium fluoride 0.65 4.12 0.65 4.10 0.25 2 Sold as c. P. sodium silicofluoride 96.63 0.25 96.78 3 Sold as sodium bifluoride 28.87 9.72 28.62 9.81
NaF Per cent 94.22 94.04 0.85 0.79 60.27 60.39
If more than 2 or 3 per cent of silicofluoride is present, the silica must be removed before precipitating the fluorine as calcium fluoride. This is done by the use of ammonium carbonate, as described by Scott in “Standard Methods of Chemical Analysis,” 4th edition, Vol. 1, p. 215, or by Treadwell-Hall in “Analytical Chemistry,” 1st ed., Vol. 11, p. 372. Notes
Other substances sometimes present with fluorine, and interfering with its determination, are calcium and barium compounds and phosphates. If calcium or barium is present, a weighed portion of the sample is fused with sodium-pGassium carbonate fusion mixture, the melt leached out with hot water, and the fluorine determined on the water extract according to the usual methods. Phosphates may be separated with silver nitrate in neutral solution, by methods similar to the one described for the separation of arsenic and fluorides. Scott (“Standard Methods of Chemical Analysis,” 4th ed., Vol. I, p. 216) describes a method that has given good results in this laboratory. Literature Cited Brinton, Sarver. and Stoppel, IND. ENQ.CHEM.,16, 1880 (1923). Dinwiddie, Am. J . Sci., 141 42, 421 (1916). Flisik, IND.ENO.CHEM.,17, 307 (1925). Katz, Ckem.- Ztg., 28, 356, 387 (1904). Rose, Ann., 62, 343 (1849). Thomson, J . ,906. Ckem. I n d . , 18, 432 (1893).
Motion Picture.Showing Manufacture of Alloy Steels “Making It Tough” is the title of an educational motion picture film just released by the U. S. Bureau of Mines, Pittsburgh, Pa., which visualizes the manufacture and uses of alloy steels. The film comprises three reels and was prepared in cooperation with a large alloy steel manufacturing concern. Copies are distributed free of charge to schools, etc., the exhibitor paying transportation charges.
