398 



SCIENCE 



[N. S. Vol. L. No. 1295 



Bourdillon.^ It was first used in tMs uni- 

 versity by Mr. M. Meacham in 1914-15 in the 

 laboratory of Dr. S. F. Acree. With this ap- 

 paratus slightly modified from the original the 

 writers have been able to secure a very good 

 grade of water by a single distillation of 

 laboratory tap water. 



Eef erring to the accompanying illustration. 

 Fig. 1 consists of a boiler and condenser and 

 Fig. 2 of an air-washing apparatus. The es- 

 sential feature of the operation of the still is 

 the washing with a stream of purified air of 

 steam and of hot condensed water while spread 

 out over the large interior surface of the con- 

 senser-tube. During operation the steam 

 passes from the boiler A (Fig. 1) through the 

 trap B and upward through the condenser- 

 tube D. At the upper end of D it is con- 

 densed and runs while still hot down the sides 

 of D to the bottom where it is further cooled 

 before being discharged into the receiving 

 vessel. During the passage through D the 

 steam and hot water are washed by a stream 

 of purified air which is forced into D at the 

 bottom and passes upward and out at the top 

 carrying with it volatile impurities from the 

 steam and hot water. The nonvolatile im- 

 purities are retained in the boiler. 



It is usual to put about one gram of KHSO^ 

 or HjPO^ into the boiler for each two or three 

 liters of water, although this may not be 

 essential. In the construction of the con- 

 denser it is better to have the workman use 

 muriatic acid rather than rosin as a flux for 

 soldering, because the latter substance may be 

 difiicult to remove from the interior after 

 completion. In the arrangement of the air- 

 washing system it is essential to have the 

 soda-lime towers between the acid jar and the 

 condenser to prevent any volatile fumes from 

 the acid passing into the condenser. It is 

 better that air be forced rather than drawn 

 through the apparatus, because this avoids the 

 possibility of contaminating the air stream by 

 leakage of laboratoi-y gases inward. The air 

 pressure obtained from the pump may be 

 regulated by varying the height of the water 

 outlet K' as well as by regulating the water 



1 Trans. Chem. Soc, 103, 791, 1913. 



supply to the aspirator. Contamination of 

 the interior of the condenser tube D from the 

 outside is prevented by inserting absorbing 

 chambers F of soda-lime and HjSO^ in 

 pumice between D' and the out-of-door out- 

 let F'. 



•By using special care and after continued 

 use for some time, water with a specific con- 

 ductivity of 0.4 X 10'^ mhos has been obtained 

 from tap water by a single distillation. With 

 a fifteen-liter boiler on an ordinary gas-range 

 burner, no difficulty has been encountered in 

 securing eight to ten liters of water per day 

 having a specific conductivity of from 1 to 

 2 X 10"" mhos. After the apparatus has been 

 started and regulated, it requires very little 

 attention. The following data are offered as 

 an example of what may ordinarily be ex- 

 pected of this still. 



TABLE I 



Specific Conductivity of Water Obtained from Tap 



Water hy a Single Distillation with Potassium 



Acid Sulphate and Phosphoric Acid 



J. p. Bennett 

 James G. Dickson 

 Botany Department, 

 TJniveksitt of Wisconsin 



SCIENCE " 



A Weekly Journal devoted to the Advancement <rf 

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