iTi' 



ujiiier parts uf the generator tubes, iiulicating' that at least one of the 

 substances still containetl moistiu'e. 



Other portions of the same mixtures as above were di'ied in their tubes 

 for several hours at lOO^-lOS". Chlorine Avas evolved upon heating- to 

 122° Imt no oxygen was evidenced by a spark. At i:>j° the rate of evolu- 

 tion of oxygen was approximately in direct proportion to the amount of 

 manganese dioxide used, this being the reverse of the case when the ma- 

 terials were not dried. This, however, is not stated as a definite law. 



Four other mixtures were more carefully dried, then heated in the 

 bath. Chlorine was evolved at 140°, oxygen at lt;8°. 



It was early seen that no relial)le results rould l)e obtained so long as 

 the manganese dioxide held moisture. To determine whether this sub- 

 stance was hygroscopic, and if so, roughly the amount of water taken up, 

 some freshly dried material was weighed in a closed bottle, then allowed 

 to stand open for definite periods, weighing after each period. In tAventj' 

 minutes its weight increased approximately 1 per cent.; after one and a 

 half hours. :! per cent.: after forty-tive hours, c. per cent. 



To determine the difference in biiiavior due to this moisture, two mix- 

 tures were prepared: In (X) the manganese dioxide was dried over a 

 free tiame, weiglicd in ;i glass-stopjiered iiottle and llie weighed potas- 

 sium chlorate .-iddcil. The other mixture (Y) was of potassium chlorate 

 and ordinary undried manganese dioxide; both were molecular mixtures. 

 In this ;ind future exix'i-inients chlorine was tested for by starch and 

 potassium iodide paper. At 125° (X) gave no chlorine or oxygen. (Yi gave 

 large quantities of chlorine but no oxygen. Much moisture collected in 

 (Yi. At 148° a steady stream of oxygen came from (Yl. continuing as long 

 as heated. No trace of chlorine or oxygen came from (X). 



More manganese dioxide Avas purified by digesting in cold distilled 

 water, then Avashing until free from chlorides. The Avash Avater contained 

 small amounts of manganese and calcium. The washed mass Avas dried 

 for two and a half hours at 20n°-210°. 



i'our tubes AA'ere now filled wifli mixtures in molecular pi'oi)orTions, 

 transferring the ni;ing:uu sc dioxide ([uickly at 2(Mi' to tlu' hot weigliing 

 bottle. co(.)ling. Avcigliing. adding tlie ground and weighed potassium 

 chlorate, and mixing. The mixtures Avere quickly transferred to the tub?s, 

 the deliA^ery tubes of AA'hich were in this case guarded AA'ith granular 

 calcium chloride. A tube of dry potassium chlorate Avas heated Avith the 

 others, in order to judge the amount of expanding air forced over. 



