Gooch and Kreider — Chlorine for Laboratory purposes. 167 



laboratory has not to our knowledge been proposed. The 

 desirability of an automatic generator from which an abundant 

 flow of chlorine gas may be drawn at will or shut off without 

 danger or inconvenience has led us to a study of the condi- 

 tions most favorable to the safe evolution of chlorine by the 

 action of the chlorate. 



Pebal* showed that the gas evolved at ordinary tempera- 

 tures from a mixture of potassium chlorate and sodium chlo- 

 ride acted upon by sulphuric acid diluted with twice its vol- 

 ume of water consists of chlorine and chlorine dioxide in 

 nearly equal proportions. Schacherlf found that when potas- 

 sium chlorate was acted upon by hydrochloric acid diluted with 

 twice its own volume of water the yield of chlorine was about 

 46 per cent or 57 per cent of the mixed gases according as the 

 chlorate was granular or in fine powder ; that hydrochloric 

 acid of half-strength yielded a gas containing nearly 60 per 

 cent of chlorine, and that the proportion of chlorine rose 

 nearly to 68 per cent when the gas was passed through con- 

 centrated hydrochloric acid and then washed with water ; that 

 the chlorate when acted upon by the strongest hydrochloric 

 acid cooled to 0° C. and then warmed only enough to start the 

 action yielded a gas carrying 87 per cent of chlorine ; and that 

 when a solution of potassium chlorate was permitted to flow 

 into hot strong hydrochloric acid the free chlorine constituted 

 nearly 75 per cent of the mixture. So it appears that the 

 highest yield of chlorine resulted when the solution of the 

 chlorate entered gradually the hot strong acid — a condition 

 not easily attained in an automatic generator. 



The fact that chlorine dioxide is so easily decomposed by 

 heat into chlorine and oxygen naturally suggests the possibility 

 of increasing the proportion of chlorine evolved in the first 

 instance by working at the highest temperatures practically 

 attainable under the conditions. In order, however, to secure 

 a temperature approaching the boiling point of water it is 

 necessary to reduce somewhat the strength of the hydrochloric 

 acid acting (in order to avoid the evolution of hydrochloric 

 acid gas and the consequent interference with the regular auto- 

 matic action of the generator), thus sacrificing the advantage 

 naturally attending the use of acid of the highest degree of 

 concentration. Upon experiment we find that acid of half- 

 strength (sp. gr. 1*10) can be made to yield a very satisfactory 

 proportion of chlorine. "We have employed in our work 

 potassium chlorate fused (best in platinum) and cast in sticks 

 or broken into coarse lumps. A small Kipp's apparatus, hold- 

 ing about a half-liter of liquid in the two lower chambers, 

 makes a convenient generator, and the requisite tenq^erature 



* Loc. cit. f Loc. cit. 



