EXPERIMENTS OF MAKING BORDEAUX MIXTURE

New Zealand Mail, Issue 1798, 22 August 1906, Page 59

EXPERIMENTS OF MAKING BORDEAUX MIXTURE

From a bulletin of the Horticultural department of Cornell University, we glean the following information regarding the preparation of Bordeaux mixture. The writer is Mr M. Y. Slingerland, and he describes four experiments which lie made. The ingredients and methods followed were:— No. 1 Dally fl best unslaked stone lime ; No. 2—Blenkhorn’s best unslaked lime; No. 3 Daily’s slaked 12 months; No. 4—Mixing the dry unslaked lime in the dilute copper sulphate. Quantities were made in proportions of 51b lime and 51b copper sulphate to 50 gallons of water. A quantity, roughly three pints of each mixture was poured into tall glass cylinder and allowed to settle for various periods. Elvery care was taken to see that the Isme had thoroughly dissolved before it was ©trained and mixed with the sulphate. On the results obtained, Mr Slingerland remarks: —“To make a good Bordeaux mixture, it is necessary that the lime he so constituted chemically as to combine with the copper sulphate and neutralise it; then it is equally as essential that the combination be mad© in such a way as to produce a very finegrained or flocoulent precipitate, which will settle very slowly, so as not to require constant agitation in the spray

pump. Suck an ideal Bordeaux mixture can fee easily made wifk any good stone lime Freshly Slaked, provided 'both' tihe lime and copper sulphate are much diluted before they are poured together.” To rgturn to my peri rnents, the mixtures were examined at one hour, three hour, and six hour intervals. Had I been, in a position to photograph the cylinders at the periods stated, my remarks would have been rendered much clearer, and the relative values - more easily seen. 1 would have it borne in mind that there were 12 mches of fluid in each cylinder. At the end of the first hour the precipitate had settled;, measuring from 1 the top of the fliriid. nr No. 1,4 in; No. 2,3 in; No. 3, No-. 4, 3&in. The flocculent appearance of Nor 1 and) 2 was 1 , very good ; themixtures hadi a- light fleecy look. „ No. 3 U although, precipitated the same as No-. 2; had! a, different appearance; the mixture seemed' to be closer in the grain, if oner may use- such an expression!. The- mixture- in No. 4 had a very compressed look, almost as though the contents- were- a solid mass. Furthermore, it was. very plain that the lime acted improperly o-n the sulphate. I need : hardly mention that a mixture so- made would he useless to- spray with. Ait the end ,of the third hour No. 1 had- preeipifabed ; 6Jin; No. 2, Sin; No. 3- sih-, and! No. 4,7 in. The same remarks* regarding Tlieir Appearances may he here made' as f-or the first hour. At. bhasendi e# six hours, No, 1 had precipitated. 7Jin; No. 2, sJin ; No. 3,. 51 in,; no notice- was. taken of No. 4. From appeajrance3. alone No. 2 ranked first, No. 1 second, and No-. 3- third. Had the lime of Not. been kept in a bag instead, of a covered cask, the result would have been poorer. To thoroughly neutralise the sulphate, more slaked lime in proportion is. required than unslaked. If unslaiked 1 lime? is not. procurable every endeavour should be- made to obtain lime a® fresh as- possible. Nothing but harm will result if haphazard methods are employed in makiilg Bordeaux mixture. A mere mixture* of lime and- copper sulphate- is- not sufficient: judgment musk be- applied.; if the best results are desired. Iron or copper vessels must never be used on any consideration, only wooden or earthenware.