Knowledge of the Chemical Elements. 189 



infusible in the highest heat of a furnace, and has a stronger affinity for 

 oxygen than any of the platinum metals except osmium. 



It thus appears that the number of elements has, during the last 

 twenty years, been increased by certainly seven or eight, and, if we include 

 the doubtful substances, by not less than a dozen. And these have been 

 discovered by a revision of the earlier investigations of chemists of the 

 highest eminence. They have all been detected in minerals of great 

 rarity, and owing to the difficulty of obtaining the raw materials from 

 which they are extracted, their properties are still very imperfectly 

 known, and offer an extensive field for further inquiry. 



But if the additions to the number of the elements are remarkable, 

 the increased information obtained regarding those of older discovery is 

 even more striking. The atomic weights of the greater number have 

 been determined with additional care, and all the refinements of the 

 improved analytical chemistry have been brought to bear upon the 

 experiments ; and while the result of these inquiries has been to confirm 

 in most instances the numbers given by Berzelius, some not unimportant 

 corrections have been introduced. 



The tendency has been to show that the atomic weights of most of 

 the elements are multiples of that of hydrogen, although some remark- 

 able exceptions to this rule have been observed. This is particularly 

 the case with chlorine, whose atomic weight is now universally admitted 

 to be 355, and not 35. 



The progress which has been made in the study of the properties of 

 the known elements is equally great, and has led to most important 

 discoveries. Perhaps the most interesting of these is the possibility of 

 obtaining an element in two diffisrent forms, in which its properties are 

 conspicuously distinct. Of these the most remarkable is that form of 

 oxygen in which it acquires a pungent and irritating odour, and the 

 property of decomposing many compounds which resist its action in 

 its ordinary state. In this form oxygen is known by the name of Ozone, 

 which was applied to it by Schonbein. He obtained it chiefly by the 

 action of the electric spark and moist air, but a French chemist, M. 

 Houzeau, has lately shown that it is obtained by the action of sulphuric 

 acid on peroxide of barium at a sufficiently low temperature. By no 

 process yet known is it possible to convert oxygen entirely into ozone, 

 and hence considerable difficulty attends the determination of all the 

 properties of the latter; but it would appear from the recent researches 

 of Andrews, that its specific gravity is four times that of ordinary oxy- 

 gen. It has been long known that sulphur varies greatly in its properties, 

 and in addition to its two crystalline forms can be obtained also as a soft 

 black substance, but it appears that it is capable of still further varia- 



