September, 1923
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
941
Powdered Bordeaux Mixture' By R. H.Robinson OREGON AGRICULTURAL EXPERIMENT STATION, CORVALLIS, ORE.
T
Equivalent amounts of HE demand for insecA method is suggested for the preparation of Bordeaux mixture ticides and fungiin which powdered copper sulfate and hydrated lime are used in the copper sdfate and hYdrated lime were used to . d e s in Powder form dry form, and recommendations are made for the commercial prepmake a 4:4:50 Bordeaux. has increased rapidly in aration of a drv - Bordeaux mixture. Since 250-cc. graduates recent years. I n every rewere employed, 2.4 grams spect the powder form is preferable. It may be put in convenient package; it is of powdered copper sulfate and 3.2 grams of hydrated lime more economical since there is a material saving in cost of were taken in all the combinations made. A few procecontainers, transportation, and deteriorating in physical dures representative of the numerous observations made properties on storage; it reduces time and labor in the prep- are as follows: aration of each tank of spray. (1) 2 . 4 grams copper sulfate dissolved in 250 cc. of water and Although the powder form is preferred, it should not be 3 . 2 grams hydrated lime sifted in. (2) 2.4 grams copper sulfate dissolved in 250 cc. of water and used if peculiar physical properties necessary for the effecgrams hydrated lime plus 0.03 gram casein sifted in. tiveness of the spray are destroyed in the manufacturing 3.2(3) 2.4 grams copper sulfate dissolved in 250 cc. of water and process. Laboratory tests substantiated by field observa- 3.2 grams hydrated lime plus 0.03 gram cane sugar sifted in. (4) 2.4 grams copper sulfate dissolved in 250 cc. of water and tions have shown that most commercial brands of Bordeaux powder are practically worthless for fungous diseases that 3.2 grams hydrated lime plus 0.03 gram glucose sifted in. (5) 2.4 grams copper sulfate dissolved in 250 cc. water and 3.2 require the toxic ingredient to adhere for several days, or grams hydrated lime plus 0.03 gram gum arabic sifted in. for months. When Bordeaux mixture is properly made from (6) 2.4 grams copper sulfate dissolved in 250 cc. of water and copper sulfate and high-grade lime, a voluminous, gelatinous 3.2 grams hydrated lime plus 0.03 gram tannin sifted in. (7) 3.2 grams hydrated lime plus 0.03 gram casein added to 350 precipitate is formed. It does not settle rapidly, and rewater and 2 4 grams copper sulfate sifted in. mains evenly distributed in suspension for several hours, cc.(8) 2.4 grams copper sulfate dissolved in 250 cc. water and 0.03 depending upon temperature, purity of materials used, and gram casein plus 3.2 grams hydrated lime containing 23.8 per care exercised in its preparation. Under the microscope cent calcium carbonate sifted in. (9) 2.4 grams copper sulfate dissolved in 250 cc. water and 0.03 the precipitate is a mass of closely connected, gelatinous gram casein plus 3.2 grams hydrated lime containing 5.0 per cent membranes. After several hours the membranes begin to magnesium carbonate sifted in. break and the suspension gradually becomes crystalline. The temperature of the water used was 23" C. The At this time the precipitate starts to settle rapidly. I n this powdered copper sulfate quickly dissolved in the water and, Condition the Bordeaux is practically worthless as a fungicide, since it is easily removed from the surface upon which it is while stirring, the hydrated lime with organic material was sprayed by rain, wind, or other agencies. If, however, sifted into the solution. Table I gives the reading on the the Bordeaux is applied when in the colloidal state, it spreads 250-cc. graduate indicating the point to which the precipitate over the surface and forms an ideal, continuous film that had settled for the stated time. TABLE I-RATE O F SETTLING OF DIFFERENTBORDEAUX MIXTURES will adhere for an indefinite length of time. Thus far no com0 . 5 hr. 1 hr. No. 2 hrs. 3 hrs. 6 hrs. REMARKS mercial Bordeaux, neither paste nor powder, that has the 240 1 246 150 Crystallized Valueless desirable properties of a high-grade product, has come to the after 3 hrs. writer's attention. Apparently, it is impossible to prevent 235 204 153 106 Good 233 213 162 115 Good the destruction of the gelatinous condition during the manu226 202 156 113 Good facturing process. 210 153 121 86 Good 84 234 Good 202 122 ~ . _ I n an effort to prepare a very high-grade Bordeaux that 80 59 49 114 Good -eact properly and settled to 64 immediately would adhere for eight or ten months under Oregon climatic 235 209 163 119 Good conditions to control anthracnose without the application With the exception of n'os. 7 and 8, all procedures gave exof the late summer Bordeaux spray, numerous different materials were added to the spray to augment its natural ad- cellent gelatinous preclpitates that indicated a high-grade hesive properties. In the course of the work it was noticed Bordeaux mixture. In No. 1, where no organic substance t h a t a good product was obtained when dry hydrated lime was used, a good Bordeaux was produced, but it began to was sifted into a tank containing the dissolved copper sulfate crystallize after 3 hours. I n the other combinations the to which a pound of casein spreader had been added. It different organic materials functioned as a stabilizer and the was thought from this observation that a good, dry, com- various precipitates retained their smooth, colloidal appearmercial Bordeaux mixture could be prepared by using the ance for more than 48 hours, when they were discarded. two separate powders, into one of which had been incorporated When a poor grade of hydrated lime, having 24 per cent some colloidal or protein material that would aid the forma- lime in carbonate form, was used, the chemical reaction tion of a gelatinous precipitate when the powders were added was retarded and a granular precipitate formed that settled to the tank of water. Accordingly, a series of experiments immediately. In addition to the procedures given above, numerous other was undertaken to ascertain the effects on the quality of the Bordeaux mixture obtained by using copper sulfate and hy- observations were made that warrant the following concludrated lime that had been treated with various organic com- sions: Impurities such as iron, aluminium, magnesia, and silica if present in small amounts have no harmful effects on pounds. the quality of the precipitate. Magnesium carbonate in 1 Presented before the Division of Agricultural and Food Chemistry small amounts is beneficial. When the copper sulfate is at the 65th Meeting of the American Chemical Society, New Haven, Conn., sifted into the lime suspension, a more granular, somewhat April 2 t o 7, 1923.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
942
coagulated precipitate forms, depending upon the fineness of the copper sulfate used. It is important, therefore, to sift the hydrated lime into the dilute copper sulfate solution. The results as a whole indicate that a high-grade Bordeaux mixture may be obtained by adding to the required amount of water, copper sulfate and subsequently hydrated lime containing a small amount of any of the organic stabilizers mentioned above It seems preferable to recommend casein as the organic stabilizer, since the natural spreading and adhering properties of this substance have been demonstrated. It is very important that the hydrated lime be as free as possible from carbonates and coarse particles. To obtain best results about 50 per cent should pass through a 200mesh sieve.
Vol. 15, No. 9
RECOMMENDATIONS FOR COMMERCIAL PREPARATIONS
It is advised that cartons be prepared containing the requisite amount of powdered copper sulfate and hydrated lime in separate packages. The packages of copper sulfate should be placed on top in order that it may be removed first when the carton is opened. Printed directions on cartons may read as follows: First, fill the spray tank with 50 gallons (for 4 pounds lime and 4 pounds of copper sulfate) of water. After starting the agitator add contents of Package A (containing copper sulfate). Then sift into the tank Package B (containing the hydrated lime plus 0.01 per cent of casein). The Bordeaux mixture is then ready for spraying.
Determination of Ash, Arsenic, Copper, and Zinc in Gelatin' By Roger M. Mehurin BUREAUO F ANIMALI N D U S T R Y ,
DEPARTMENT O F A G R I C U L T C R E , WASHINGTON,
D. C
T
HE laboratory in-
Undesirable features of published methods for the determination out and combined SO as to of small quantities of arsenic, copper, and zinc are pointed out, and form a coherent method by spection of meats, ' a coherent, rapid, and accurate method for the determination of which accurate results are meat food Products, obtained with a minimum and substances used in conash, arsenic. copper, and zinc in gelatin is described. nection with their preparaSources of possible error are enumerofed SO that the method will expenditure of time and tion involves the analysis be adaptable for inexperienced analysts. labor. This method in subof numerous samples of stantially its present form has been in use in the meat gelatin. I n order to make certain that gelatin of suitable quality is used, samples are inspection laboratories of the Bureau of Animal Industry for collected from each shipment received at any establishment a t several years. which federal meat inspection is maintained, and are subARSENIC mitted to the laboratory for examination. During the last REAGENTS-Dilute hydrochloric acid: Dilute one part arsenicyear, 247 such samples were examined in the Washington free hydrochloric acid (sp. gr. 1.19) with 3 parts distilled water. Potassium iodide solution: 600 grams per liter. Meat Inspection Laboratory. Chief among the objectionStannous chloride solution: Dissolve 50 grams in 50 cc. arsenicable impurities found in gelatin are arsenic, copper, and free hydrochloric acid (sp. gr. 1.19) and dilute to 200 cc. with diszinc. These metals are usually present in amounts not tilled water. Bromine water: Saturated, keep an excess of bromine in the exceeding 1.4, 30, and 100 parts per million, respectively. All the available methods for the determination of arsenic, bottle. Lead acetate cotton: Moisten the cotton with 10 per cent lead copper, and zinc in food have been tried out, but have been acetate solution and dry. found unsatisfactory when applied to the determination of Mercuric bromide paper: Prepared by dipping a small sheet these metals in large numbers of samples of gelatin. The of hard-surfaced drawing paper into a 5 per cent alcoholic soluof mercuric bromide, drying so as to obtain as uniform demethod described in the Methods of Analysis of the Asso- tion posit as possible of the mercuric bromide, and cutting the sheet ciation of Official Agricultural Chemists, involving digestion into strips 2 x 70 mm., preferably in a cutting machine prepared with sulfuric and nitric acids, is entirely unsuitable on ac- for this purpose. METHOD-weigh out 10 grams gelatin into a 150-cc. beaker. count of the excessive frothing, the time required for comAdd 50 cc. dilute hydrochloric acid and place on steam bath. plete oxidation, and the continued exposure of the analyst to As soon as gelatin is dissolved add 20 cc. bromine water. After irritating fumes. The methods employing hydrolysis with digesting for one hour remove from the steam bath and cool. hydrochloric acid have likewise proved unsatisfactory on Make up solution to 100 cc., mix, and filter. To 20 cc. of the account of difficulty in saturating with hydrogen sulfide and filtered solution add 1 cc. potassium iodide solution and 0.3 cc. stannous chloride solution. Heat on steam bath for 5 minutes, the subsequent filtering of large volumes of solutions which are cool, and transfer to a previously prepared Gutzeit apparatus. often of such a character as to filter slowly. The determina- Prepare this apparatus as foIlows: Add to the generator 3 grams tion of copper by titration with sodium thiosulfate is open to 30-mesh, arsenic-free zinc and 20 cc. dilute hydrochloric acid; a considerable error because of the difficulty of obtaining a connect and allow t o run for 5 minutes. Place a small amount of loosely drawn lead acetate cotton in the barrel before connectdefinite end point when small amounts are titrated. The ing the apparatus and a strip of mercuric bromide paper in the employment of Gooch crucibles in filtering and weighing small tube just before adding the solution. Add 0.8 cc. amyl alcohol, amounts of zinc has sometimes been found to be a source of rinse out beaker with 3 to 5 cc. water, and add to generator. The liberated gases pass through the lead acetate cotton and error. over the strip of mercuric bromide paper. Allow generator to The method described below has developed as a result of run for one hour, or longer if necessary, protecting paper from several years' experience in the analysis of gelatin and is free strong light. Compare with standards prepared in the same from any and all of the faults cited. While it utilizes only well- manner from arsenic-free gelatin to which known amounts of known analytical procedures, the details have been worked arsenic have been added. Standards should show the action of 1
Received March 28, 1923.
from 1 to 7 micromilligrams (0.001 to 0.007 mg.) of arsenious acid (Asz08).
