ROOT CROPS. 1-99 



Samples of Milestone sometimes come on th<- market which contain a 

 quantity of sulphate of iron, and it is as well that the farmer should 

 know the difference. Bluestone proper should be in the form of dark blu< 

 crystals, while the adulterated mixture is a lighter blue ; indeed, the charai 

 teristic colour of sulphate of iron is a light green. The bluestone may be 

 tested by dissolving a tV« crystals in water and adding a little ammonia. A 

 pale blue precipitate is formed which dissolves to an intense blue colour, and 

 the solution remains perfectly clear and free from sedimenl if allowed to stand 

 for a while. It a reddish sediment settles, it is due to the presence of iron. 



It is of importance that the lime should be freshly burnt. To test whether 

 it i-> so, a few lumps should he placed in a heap and sprinkled with water. 

 If freshly burnt, these will gradually fall to pieces, becoming very hot in the 

 process, giving offa quantity of steam, and crumbling to a fine, white powder. 

 If it does not get hot enough to give off steam it has not been freshly burnt. 



The first operation in making Bordeaux mixture is to dissolve the coppei 

 sulphate and to make the milk of lime separately. It is for this that the 

 smaller vessels are required. 



It is a common practice is to crush the bluestone crystals and then to 

 pour boiling water over the powder. To dissolve the 6 lb recommended in 

 the above formula, 2 gallons of hot water should be sufficient. When it is 

 seen that the bluestone is dissolved, cold water should be added to bring up 

 the quantity to half the total quantity of spray to be made. That is to say, 

 if 2 gallons have been used to dissolve the 6 lb. of copper sulphate, then 

 23 gallons will have to be added so as to bring the water up to 2-3 gallons, 

 which is half the total quantity to be made. Farmers often omit this last 

 point, simply obtaining the solutions and mixing" them before adding the 

 requisite quantity of water ; but the practice has a distinct effect upon the 

 quality of the spray mixture, lowering its efficiency and increasing the 

 probabilities of the nozzles becoming clogged. 



It is not essential to dissolve the bluestone in hot water. Half the water 

 (that is 25 gallons if 50 gallons are being made) can be put in the cask, 

 and the bluestone suspended in a porous sack, as near the surface as possible. 

 If thrown loose into the bottom of a tub of cold water bluestone will net 

 dissolve in a week. 



If large quantities of Bordeaux mixture aie being used, it is handy to 

 make a concentrated solution of copper sulphate and to use it as required. 

 Such a stock solution of copper sulphate (bluestone) can be made in a large 

 cask, of a strength, say, of 1 lb. to 1 gallon of water. This can be done by 

 weighing out the desired quantity of copper sulphate, and suspending it in a 

 piece of bag or hessian in the upper part of a measured quantity of water. 

 A\ hen mixing the spray, a gallon of this solution is used for every pound of 

 copper sulphate required. A mark should he made at the level of the liquid 

 after removing any of the stock solution, so that if evaporation occurs it can 

 be compensated for by the addition of more water. 



The lime, which as stated above should be freshly burnt, is slaked by the 

 addition of about half a gallon of warm water. Sufficient water must he 

 used to ensure the whole of the lime being slaked, and it should he added 

 from time to time in small quantities, to keep the action even and ensure 

 perfect slaking. It is a common mistake to add too little water at this 

 stage, with the result that too much heat is developed and the lime is 

 burned, in which case there are many small lumps that do not slake down 

 properly, and they have to be thrown out in the straining to prevent the 

 nozzle becoming clogged. 



