288 Agricultural Gazette of N.S.W. [April 3, 1920. 



2. The treated beds are entirely free from weeds, and presumably from 



fungus spores. 



3. The operation is a lengthy one, but the subsequent freedom from 



weeds is a consideration. 



4. No absolute immunity from " blue mould " can be expected unless the 



whole of the seed-beds and those on adjacent lands are treated, 

 and unless workmen from infected areas are prevented from 

 visiting the beds. 



" Leaded Bordeaux " Spray : an Analysis. 



An analysis of Leaded Bordeaux shows the following composition : — 



Per cent. 



Lead oxide 38*47 



Arsenic acid ... ... ... ... ... ... ... ... 15"95 



Lime 17-31 



Copper (4"32), expressed as crystallised copper sulphate ... 16"96 



Carbonic acid ... ... .. ... ... .. ... 2'05 



Oxides of iron and aluminium ... ... ... ... ... 1-26 



Not determined 8"00 



100-00 



The lead arsenate present probably exists in combination as 30-67 triplumbic 

 arsenate with 24*37 diplumbic ar.senate ; or, expressed in another way, 55*72 

 per cent, of the lead arsenate present exists as triplumbic arsenate and 44*28 

 per cent, as diplumbic arsenate. The preparation therefore consists essentially 

 of 55 per cent, of lead arsenate, 16 -96 per cent, crystallised copper sulphate, 

 and 14 7 per cent, of lime, excluding what is pi-esent as carbonate and 

 useless for the preparation of Bordeaux mixture. 



According to the formula for preparing Bordeaux mixture recommended by 

 this Department in Farmers' Bulletin No. 72, page 31, namely, 6 lb. bluestone 

 with 4 lb. lime, the above amountof bluestone (16*96) should require 11*3 lb. 

 lime, whereas 14*7 is present. This slight excess of lime may possibly be 

 introduced to compensate for any change in the lime from oxide or hydroxide 

 to carbonate. 



According to instructions issued with the preparation, 2, 3 or 4 lb. should 

 be used to each 50 gallons of water ; 32*7 oz. of Leaded Bordeaux would 

 contain 18 oz. of lead arsenate (which is the strength for lead arsenate 

 spraying recommended by the Department). This amount (32-7 oz.) of the 

 preparation would at the same time contain 5*55 oz. bluestone, the equivalent 

 of which would be contained in 50 gallons spray. The Departmental Bordeaux 

 mixture, 6-4-50, would contain the equivalent of 96 oz. bluestone per 50 

 gallons, 30 that the Bordeaux produced by the preparation under notice would 

 be in this ca.se about 17 times too weak. 



If 4 lb. Leaded Bordeaux be used per 50 gallons, the strength of the lead 

 arsenate would be twice that recommended by this Department, and the 

 strength of the Bordeaux would be about 8i times too weak. — A. A. Ramsay, 

 Principal Assistant Chemist. 



