BAIRD &. TATLOCK (LOM)ON) LTD. 



The apparatus consists of two parts a still and condenser, see Fig. i. 



Fig. 2. The Condenser consists of a box of sheet copper with a lid which has four openings with inclined 

 sides. These support four test tubes cooled by circulating water. Through two of the tubes a rapid flow of water 

 passes, and from these the best water is collected by means of funnels i and 2. Through the other tubes water 

 passes very slowly and is used to feed the still, and serves also to condense a small quantity of water collected 

 by the funnels. About one-third of the water distilled condenses on the surface of the copper box, and is 

 collected from the copper tube. This is the lowest quality, and is good ordinary distilled water. 



The Water. The conductivity of the best water produced depends to some extent on the conditions under 



which the still is used. The addition every two or three days of a little alkali to the still in order to retain carbon 



dioxide was found to be an advantage, or in the alternative, the addition of potassium hydrogen sulphate to 



keep back ammonia and basic impurities. Under these conditions the normal product of the coolest tube is 



m -in mho- water " (X = i x 10 ), and this can be produced in any desired quantity. By storing this water in a 



Ian,'<' bottle in contact with air, freed from carbon dioxide by means of lime, its conductivity can be reduced to 



and can be further improved by boiling. 



No advantage is derived from condensing the purified water on platinum instead of glass tubes, provided 

 that soft glass is not used. A very great improvement results, however, if the purified water is boiled for a few 

 minutes in a platinum bottle. In one instance a sample of water that had an initial conductivity of 0.84 x 10 

 at 18 was reduced by boiling for two minutes to 0.48x10 ', representing an exceptionally high degree of 

 purification. 



The still can also be used for the preparation of ammonia free water and copper free water. 



Fig. 3. A specially designed still to prevent spray being carried over with the steam. The copper cylinder 

 is furnished with a branch pipe A. B is the opening into which the water is fed continuonsly, the excess escaping 

 at F. The spray, which is driven against the baffle-plates, runs down the sides of the funnel D and back into the 

 water below. An external covering EE serves to economise the heat of the burner. 



OF 



5287 (Section) 



5287 



5287 s Bousfield's Pan Still (Patent Application No. 14223, 1912) 



This still produces water of a conductivity of less than i gemmho practically free from ammonia, by 

 continuous fractional distillation from ordinary " tap-water." (See Journal Chemical Society, August, 1912.) 

 It may be run continuously day and night, and with a yj inch pan will yield daily about 20 litres of 

 " conductivity water " and 10 litres of ordinary good distilled water. One of these stills will thus supply all the 

 ordinary requirements of a laboratory, and the bulk of the product is suitable for conductivity and analytical 

 work of a high degree of accuracy without additional expense. 



The open pan construction is extremely convenient, as it enables the apparatus to be readily cleansed from 

 scale or other deposit which collects in the pan. But the part which the open pan plays in purification is more 

 essential. Feed-water is supplied in the open annulus between the pan and the cylinder. It has gradually tc 

 make its way downwards until it passes underneath the bottom of the open cylinder into the interior. During 

 this passage from the exterior to the interior, the organic impurity of higher boiling point, which e 

 ordinary water, is largely decomposed before the liquid reaches the interior of the cylinder, so that the ammonia 

 thus liberated, and also the carbon dioxide and dissolved air contained in the water, are boiled off and escap< 

 into the open air instead of passing through the still. This feature materially contributes to the improved results 

 which this still gives 



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