CHLORINE 3c; 



for the left hand member for each successive hundred units of pressure, 

 namely: 114, 106, 96, 87, 81. Similar, though somewhat lower 

 results are found if an additive instead of a proportional relation is 

 assumed. 



Another method of computing any property of chlorine is by extra- 

 polating that property of bromine and iodine. 



In some cases, such as the atomic weights and volumes, the relation 

 is almost linear ; in such cases extrapolation of this kind is moderately 

 accurate in its results. Compressibility, being a volume function, may 

 also be assumed to vary in approximately linear fashion. Upon this 

 assumption, the compressibility of chlorine would be that of bromine 

 plus the difference between that of bromine and iodine. The values 

 thus obtained agree surprisingly well with those given above, as may 

 be seen from the following table. 



Probable Compressibility of Chlorine at 20 C. 



This curve is plotted in a dotted line on the diagram (Fig. 5). It 

 makes no pretensions to accuracy, but serves to give an approximate 

 idea of the probable magnitude of the quantity in question. It will be 

 seen that chlorine is probably nearly twice as compressible as bromine 

 and thirty times as compressible as mercury. 



Phosphorus. 



The material used was the purest commercial pale yellow phophorus, 

 which was fused under water and cast into sticks of suitable size. 

 These sticks were cut into lengths of about half a centimeter each, in 

 order to disclose occasional cavities. All imperfect pieces were of 

 course rejected. The specific gravity, according to the recent deter- 

 minations of Pisati and de Francius, 1 is 1.823. The phosphorus was 

 weighed under water after washing with alcohol and ether and drying. 



Phosphorus attacks mercury too vehemently to be immersed directly 

 in the mercury of the glass jacket. It was therefore packed into a 

 thin glass tube containing water ; and in order to be handled more 



1 Berichte d. deutsch ch. Ges. 8, 70 (1875). 



