INDUSTRIAL A N D ENGINEERING CHEMIXTRY
November, 1923
1177
111-EFFICIENCYO F METHOD FOR REMOVAL OF INTERFERISG UREA TABLE11-EFFICIENCYOF METHOD FOR REMOVAL OF CYANAMIDE, DICYANO- TABLE NITROGEN DIAMIDE, AND GUANYLUREA (Added urea nitrogen = 8.35 mg.) (Added organic nitrogen = 8.35 Mg.) Added Organic Nitrogen Appearing Added Urea Nitrogen Appearing as Nitrate Nitrogen as Nitrate Nitrogen Mg. Per cent NITROGMN COMPOUND Mg. Per cent 0.092 0.031 0.37 0.045 Cyanamide
Av. Dicyanodiamide
Av. Guanylurea sulfate
Av. Urea Av.
0.023 0.057 0.031 0.035 0,023 0.031 0.031 0.040 0.031 0.065 0.098 0.040 0.048 0.063 0,452 0.528 0.490
0.27 0.68 0.37 0.42 0.27 0.37 0.37 0.47 0.37 0.78 1.17 0.47 0.57 0.75 5.41 6.32 5.86
0.019 0.019 0,027
Av.
0.040
TABLE IV-RECOVERYOF NITRATE NITROGEN IN PRESBNCE OF CYANAMIDE
AND SOMEOF ITS DERIVATIVES (Added nitrate nitrogen = 3.89 mg., added organic nitrogen = 8.35 mg.) ORGANIC NITROGEN Added Nitrate Nitrogen Recovered COMPOUND Mg. Per cent None 3.930 101.03
Av. Cyanamide
of orgmic nitrogen. In order to determine the efficiency of the procedures as regards the recovery of added nitrate nitrogen in the presence of the organic nitrogen compounds, soil extracts were prepared in the same manner as those previously used. Aliquots containing 3.89 mg. of added nitrate nitrogen in the form of potassium nitrate and 8.35 mg. of' added organic nitrogen were analyzed by one of the procedures dependent upon the nature of the organic nitrogen presenc.
Av. Dicyanodiamide
Av. Guanylurea sulfate Av. Urea Av.
3,920 3.925 3.894 3.928 3,955 3,898 3.919 3.932 3.974 3.879 3.960 3.936 3.896 3.852 3.874 3.886 3.877 3.919 3.894
100.77 100.90
101.08 102,16 99.71 101.80 101.19 100.16 99.02 99.59 99.89 99.66 100.74 100.10
Colloidal Copper Hydroxide as a Fungicide' By Henry D. Hooker, Jr. UNIVERSITY O F MISSOURI, COLUMBIA, Mo.
A
'r PRESENT there is no entirely satisfactory fungicide
available. The two most important ones are Bor. deaux and lime-sulfur, but both burn the foliage under certain climatic conditions, and neither is remarkable for its sticking or spreading properties. Bordeaux is difficult to prepare correctly and the ready-made mixtures on the market have not proved ideal. Lime-sulfur does not control some fungus diseases, such as apple blotch, and consequently fruit-growers must supplement lime-sulfur spraying by subsequent applications of Bordeaux where this disease is prevalent. Lime-sulfur is, moreover, a most disagreeable material to handle. It was thought that a colloidal copper compound would prove an ideal fungicide. If a material having a positive electrical charge could be prepared, it should have in colloidal isuspension the sticking and spreading qualities of lead arsenate. It was thought that the burning properties of Bordeaux might be eliminated by preparing an insoluble compound such as copper hydroxide in colloidal suspension because plant membranes are impermeable to colloids.
PREPARATION OF COPPER HYDROXIDE Colloidal copper hydroxide was prepared by using a modification of the method reported by Bradfield2 for the preparation of colloidal iron hydroxide, aluminium hydroxide, and silicic acid. A 10 per cent solution of sodium hydroxide was added to a solution of copper sulfate with constant stirring until the supernatant liquid lost its color. Copper hydroxide was thrown down as a pale blue precipitate. An excess of alkali leads to the formation of a deep blue precipitate which changes on standing to black copper oxide. 2
Received July 23, 1923. J. Am. Chem. Soc., 44, 965 (1922).
This must be avoided and it is better to leave some copper sulfate in solution than to attempt to reach an end point. The mixture so prepared contains sodium sulfate, a small amount of copper sulfate in solution, and a precipitate of insoluble copper hydroxide which holds, probably by adsorption, a considerable amount of copper sulfate. The preparation of colloidal copper hydroxide depends on the removal of the electrolytes-namely, the copper sulfate and sodium sulfate in solution and likewise a large part of the adsorbed copper sulfate. This was accomplished by agitation and repeated washing by sedimentation. Distilled water was used. When first thrown down by the addition of sodium hydroxide solution, a mixture was obtained that was far from homogeneous. This was pumped under pressure with a hand pump through a spray nozzle from one receptacle t o another, to break up the precipitate and render the mixture as homogeneous as possible. This procedure was repeated after every few washings. The mixture was transferred to a tall glass vessel and allowed to settle for 24 hours. The supernatant liquid was siphoned off, distilled water was added, and the whole was mixed thoroughly by vigorous stirring. After a dozen such washings by sedimentation practically all the free salt was removed. As long as the copper hydroxide was washed in relatively small volumes of water-50 parts of water by weight t o one of copper hydroxide-the supernatant liquid remained clear. After the free salt had been removed, the volume of wash water was increased to 200 parts of water by weight to 1 part of copper hydroxide, and the process of washing by sedimentation continued. After several washings the precipitate settled, leaving an opalescent, supernatant liquid. This contained a very small amount of copper hydroxide, which settled out after standing for
INDUSTRIAL AND ENGINEZRING CHEMISTRY
1178
several days. As the washing was continued the amount of copper hydroxide remaining in suspension after the settling of the larger particles increased until what might be termed an incipiently colloidal solution was obtained which contained 1 part by weight of copper hydroxide in 1000 of water. At this concentration and dispersion the solution foamed readily on shaking. This was the maximum concentration and dispersion obtained by the process described. The material so prepared is a delicate robin’s-egg blue by reflected light and blue-green by transmitted light. The copper hydroxide remained in suspension for several weeks, but the solution became stratified. By centrifuging in a supercentrifuge the copper hydroxide is thrown out. This may be ground up with small amounts of water, resuspended, and shaken according to the Bradfield procedure. After centrifuging a few times a true colloidal solution can be prepared. Various modifications of this method might be suggested. It would undoubtedly require fewer washings to prepare colloidal copper hydroxide from a monovalent salt such as copper chloride. Several devices might be used to remove larger percentages of water from the copper hydroxide than is possible by sedimentation, thus making each washing more thorough. The addition of small amounts of acetic acid will peptize the copper hydroxide. The object of this work, however, was to prepare colloidal copper hydroxide from the cheapest materials by the simplest procedure. If a supply of soft water had been available, this would have been used instead of distilled water, thus reducing still further the cost of manufacture, SPRAYING EXPERIMENTS Two distinct types of copper hydroxide were used in the spraying experiments. One was a sediment from which all free soluble salts had been washed, but which showed no tendency to go into colloidal suspension. When washed in a large volume of water it settled out quickly, leaving a clear supernatant liquid. The other was an incipiently colloidal preparation purified as far as possible by the sedimentation method. This material remained in suspension for a long period and foamed when shaken. Experiments were carried out in a neglected apple orchard that had not been sprayed for several years. The materials were used in the following concentrations: Trees
COFPBR HYDROXIDE: Sprayed Sediment: 1st dilution.. . . 2nd dilution.. 3rd dilution.. . 4th dilution.. . Colloid: 1st dilution.. . . 2nd dilution.. 3rd dilution.. .
. .. .... ..... ... . .. .. .. .. . .
Concentration
%
Parts by Weight of Water t o 1P a r t Cu(0II)2
Copper Used Conipared with3:4:50 Bordeaux
0.4 0.2 0.1 0.05
260 500 1000 2000
143.0 71.5
0.076 0.038 0.019
1315 2630 5260
%
35.8
Vol. 15, No. 11
When the last spray was applied it was observed that all t h e apples in the trees sprayed with the copper hydroxide sediment had been burned, presumably by the first application. Contrary to expectations the first dilution of the colloidal preparation produced exceptionally severe burning; the second dilution gave burning approximately equivalent to the 3 :4 : 50 Bordeaux; .the lowest dilution produced very little burning, not much more than lime-sulfur. The first dilution of the sediment gave severe burning, though not so severe as the strongest concentration of the colloid; the second burned about equal to 3:4:50 Bordeaux; the third and fourth, slightly less. It was distinctly noteworthy that dilution of the colloidal preparation reduced burning to a greater extent than did similar dilution of the sediment. On July 12 the fruit was removed from each of the sprayed plots and from check trees to determine the fungicidal value of the sprays. The unsprayed fruit showed both apple scab and apple hlotch. Approximately 20 per cent of the fruit was diseased, 13 per cent by scab and 7 per cent by blotch. The fruit on all sprayed trees was clean, not a single sign of scab or blotch being found on any of the apples from trees sprayed with copper hydroxide. The trees treated with the first dilution of the sediment and of the colloid had lost all their apples, apparently as a result of the severe burning. The fact which merits emphasis is that under the conditions of the experiment complete protection from both scab and blotch was afforded by the weakest concentration of the colloidal copper hydroxide used and that this spray produced very little burning, much less than 3: 4:50 Bordeaux and very little more than lime-sulfur. The amount of c o p per used was one-fifteenth that used in 3: 4:50 Bordeaux. These preliminary tests would indicate, therefore, that a great saving in the cost of fungicidal spray materials could be made by using prepared colloidal copper hydroxide. Should the results be confirmed by subsequent tests under a wide variety of climatic conditions, 1 pound of copper as colloidal copper hydroxide would suffice to spray 2 to 3 acresqof apple orchard once. It is, of course, possible that an even more dilute concentration may give adequate protection and no burning. Additional experiments on a small scale have shown that colloidal copper hydroxide can be mixed with nicotine sulfate. A colloidal solution containing 1part of the hydroxide in 5000 parts of water was sprayed on one peach tree and on one cherry tree. This work was done with a hand pump and a rod with a disk nozzle. No evidence of burning on either kind of fruit could be found. However, no additional information concerning the fungicidal properties of copper hydroxide was obtained.
17.9
.
27.0 13.5 6.8
The trees sprayed were Ben Davis. A power spray was used and the material was applied with a spray gun. The first application was a calyx spray on May 11. This was followed by sprays on May 21 and June 4. On the two latter occasions lead arsenate was added at the rate of 3 pounds of powder to 100 gallons of spray. Fifteen trees in the same orchard were sprayed a t the same time with 3 :4 : 50 Bordeaux and fifteen others with 3: 100 lime-sulfur. Alarge number of trees were left unsprayed as checks. The only water supply available for diluting the spray material was a muddy stock pond. This water was used, though clear water would have been preferable, as mud is a negative colloid and throws copper hydroxide out of suspension. The early part of the season was characterized by cool, wet weather, particularly favorable to Bordeaux burning.
CONCLUSION Preliminary experiments indicate that copper hydroxide prepared as a colloid is fungicidal to apple scab and apple blotch in concentrations of 1 part of hydroxide to 5000 of water. At this concentration it produced very slight burning. It has excellent sticking properties due to its positive charge and spreads well in dilute solution. It can be used in conjunction with lead arsenate and nicotine sulfate. Although it would be hazardous to estimate the cost of manufacture, it is clear that colloidal copper hydroxide would be much less expensive than either Bordeaux or lime-sulfur. From Germany comes announcement of the death of P. Friedliinder, privat-dozent for organic chemistry and technical organic technology in the Technical Hochschule a t Darmstadt. Professor Friedldnder is well known for his investigations on the chemistry of dyestuffs and for his work “Fortschritte der Teerfarbenfabrikation,” which appeared in twelve volumes.
