NEED FOR SPRAYING.

Dominion, Volume 5, Issue 1332, 9 January 1912, Page 8

NEED FOR SPRAYING.

, PKEPAIUTION 01- , HOKDEAUX MIXTURE. The frequency with which experts advisu spraying with Bordeaux mixture as a preventive of blights, elc, lends particular interest to some instructive information given by Mr. ]{. Waters in the Agricultural Department's -Journal regarding tho most efficacious method' of preparing tho mixture, Mr. Watcxs says: Purity of Materials. In the successful preparation of-Bor-deaux it is of first importance that the materials shall be of good quality. The essential ingredient in Bordeaux nrixturo is sulphate of copper, commonly known as "Milestone." Tins compound is liable to be adulterated with sulphate of iron, a crystal of greenish appearance. The purchaser should endeavour to obtain Milestone known to be of not less thau !)8 per cent, purity. The following is, a useful purity test for Milestone: Take a, very small piece of bluestone, crush it to a powder, place it in a cuy, and dissolve in a little, boiling water; then pour into <i glass unci add small quantities of strong ammonia, drop by (bop. This will causo the formation of light-coloured blue clouds in the liquid. Continue adding ammonia, when, if tho Milestone is pure, tho clouds will disappear and tho liquid become thin and change to a rich blue. If, on tho ammonia being added, the liquid, instead of .shuwiug blue clouds, becomes-brown-black, and repulsivo looking, it .-vows the prcseifce of largo quantities of iron, and should not be used. Now, if i\ solution of pure Milestone, say Jib. to 50 gallon.? water, were applied to foliage, it would, on account of its'acid qualities, cause sorions injury—"burning" as it is called. In the preparation of Bordeaux mixture an alkali is therefore used, preferably lime, though in its al)- . senco common washing soda is substituted.. The alkali causes the formation of a harmless (basic) sulphate of copper. 'Lime Bordeaux is, however, very different from' soda" liofdeaux, which may only'be used in certain special ca?cs. Wine should, bo procured freshly burnt and in an ini-' slaked condition. In this form it is known as "quicklime," "burnt limp," "unslaked lime," and "reche lime," and is-obtained by tho• "burning" of limestone; in a kiln. Certain dealers now stock quicklime for swaying purposes in sealed tine to ensure it reaching the purchaser in an unslaked condition. Exposure to such air-siaked lime is useless " for the manufacture of Bordeaux mixture. Quicklime .ts offered to the public varies considerably as to its purity. The quantities of lime prescribed (ire' calculated to allow for all reasonable variation in this commodity. ' It will bo easily seen, however, that very impure lime, from its deficiency in alkaline quality, would fail to completely convert the bluestone into the harmless comiioimel, with the result that "burning" would follow. If a. lumn of good quicklime is saturated with water, particularly hot water, it will in a short time evolve much steam and heat, and finally cruinblo to a- fine snow-while powder. Impure lime, on the other hand, is slower in its action, anl a quantity of rock} material will remain when the slakin;,' has censed. The 'water use.'l for the manufacture of Bordeaux should bo us nure ns possible; rainwater is preferable. ' The Making, First the bluestone and the lime shculd bo reduced to liquid form. This is done separately, half the total quantity of water being used for each ingredient. The bluestone may be tied in a niece of sacking and lie suspended overnight just below tho surface of a few gallons of water. If placed in the bottom of a barrel or other receptaclo it dissolves much slower,even though frcmientiy stirred. Tor quickness it may ho dissolved in a small quantity of hot water.. The Solution should then bo made up to half tho total quantity of water required fir tlin wash.' 'I'llß lime should first be slaked by tho addition of small quantities of water—the uso of a little hot water in tho first place will give it a start; it should not be immersed, nor should so little water be supplied that excessive evolution of heat continues. When the breaking-down of the lumps has started small quantities of cold water should be added from time to time as required, lirst for the purpose of supplying the quantity necessary to completely disintegrate the lumps, and second lo keep the lime moist and prevent undue drying and heating. When all the linie has slaked sufficient water should bo added—a little at a time, stirring well—to form a thick smooth paste. Further additions of water should then gradually bo nrade—stirring briskly—to convert this paste into a. milky consistency, and finally to bring it up to half the total quantity of water in the wash. It is likely that the limo will be mixed moro or less with rocky material, etc., that will not slake; to remove all such particles that would block the pump in spraying, strain tho milk of' lime —using a fino wire strainer as it is poured into the bluestono solution. It -is important that the milk of lime should '.bo well stirred just before straining into the bluestone solution, and that tho mixture should aho be stirred vigorously while the inilk of limo is gradually added, and afterwards for a few minutes. \ The mixture will quickly become cloudy with the bluish compound which is precipitated iu the chemical action that takes place. By mixing in this manner the precipitate formed will maintain its suspension in the water—i.e., it will not quickly, settle—and thus facilitate even distribution in spraying. Slightly better suspension may bo obtained by pouring the bluestoue solution and the milk of lima at the same rate into a third vessel; where practicable this course will probably be found tho best. If there is an excess of Milestone— that is, , if the actual -quantity of -pnre lime used was insufficient —the mixture will 1)0 an acid one, and probably injurious to foliage. The aim should bo to obtain either n neutral mixture —i.e., one which is neither acid nor alkaline—or else a slightly alkaline one. The effect of too much lime, however, will bo to causo delay in the fungicidal action of tho mixture, owing to the formation of a compound (basic calcium-sulphate) which must bo decomposed by the carbon-diox-ide in the air. before tho copper compound, which is afterwards similarly decomposed, can effect its purpose. It has been further asserted that neutral, mixtures, are, . superior to alkaline unes in l their'power of adhering to fuliagc. Testing the Spray. The following are several methods of tesling tho spray, any one of which will be found of value in ascertaining whether the mixture i- .v\fr> for use:— 1. If the blade of a clean bright knife dipped into the spray f»r about a minute should become marked with a reddish stain of copper, it is "apparent that there is an exenss of blur-stone, and that u further quantity of lime should be added; if the blade remains micluingpcl, the mixture is .safe for use. 2. Place a small quantity of wash in n bowl, and breathe upon tho fluid for about a minute; the formation of a delicate film on the surface indicates that tho mixture is alkaline—that is, that there is an excess of lime. The film can host bo seen when the liquid is so placed that the surface reflects tho light to the eyes. . ' . . 3. A good test for the presence of nnprccipita'.cd copper may also be made ns follows: Place 'a small quantity of the wash in a tumbler, and add to it a few drops of a solution of yellow prussiate (potassium ferro-cyanide, 10 per cent toution). obtainable -from a chemist. If the quantity of limo is insufficient the test solution turns reddish-brown soon after it comes in contact with the Bordeaux mixture, indicating (hat more limo should bo added. When more lime is required, add it as before in the form ofmilk of lime through ii strainer, stirring wall. The additiim of lirne should be continued until tho test, solution when added remains clear. This test will bo m-jr? cn-ily nbsm-vccl if the wa,-h n-c<] is M'udori-d clear by running it through a lilt 1. , : , paper. Utensils. Woc.lc-ii or rnrihenwarc voxels should I be used in the preparation o:' the mixI tun-. Blue-lone quickly cate iiitu vessels