CHEMISTEY. 



119 



If all the elements, after hydrogen, with 

 which the law has been verified, are arranged 

 in the order of their atomic weights, they will be 

 found to divide themselves into two kinds of 

 periods or groups : the smaller periods, of which 

 there are two, including seven elements each, 

 and the larger periods, seventeen elements each. 

 The grouping and the distinction of the pe- 

 riods are based upon and justified by the fact 

 that the several members of a single period 

 show no similarity or community of properties 

 and chemical character with one another ; but 



after that period closes, another period begins, 

 the several members of which show an unmis- 

 takable parallelism with the corresponding 

 members of the previous period. Arranging 

 the periods in parallel columns, we shall find 

 that the elements standing on the same hori- 

 zontal line in every case exhibit similarities in 

 chemical and physical character, and would be 

 at once recognized as allied with one another. 

 This is shown by the following table of the pe- 

 riods, which we take from an article by Victor 

 Meyer in the "Deutsche Rundschau": 



The only seemingly exceptional case observa- 

 ble here is in the position of carbon aod silicon, 

 whose relationship to titanium and zirconium 

 on the one side, and to tin on the other, is in- 

 dicated by the dotted lines; but it will also be 

 noticed that the symmetry of the table is still 

 perfect. The first line, it will be observed, 

 contains the five alkali metals lithium, sodi- 

 um, potassium, rubidium, and caesium between 

 which relationships had already been recog- 

 nized in their constituting a double triad, and 

 which are known as the most electro-posi- 

 tive of all the elements; while the last line 

 contains the four extremely electro-negative 

 halogens elements exhibiting quite as strik- 

 ing similarities in all properties with one 

 another as those of the first line. Similar cu- 

 rious relations may be detected in the ele- 

 ments represented in the other lines, and a 

 gradation of electro - chemical properties ob- 

 served down the columns. When the table 

 was first made, there were two more gaps in 

 it than now appear. They were filled by the 

 discovery of scandium by Nil son, and of gal- 

 lium by Lecoq de Boisbaudran, with atomic 

 weights fitting them to places that were in- 

 dicated for new elements, and possessed prop- 

 erties, as determined by experiment, which 

 corresponded with those which Mendelejeff had 

 predicted that the elements that should occu- 

 py these places should possess. 



Investigating the conditions of the color of 

 chemical compounds, Professor Carnelly has 

 found them dependent on three circumstances, 

 the first two of which were previously de- 

 termined by Ackroyd 1, temperature ; 2, the 



quantity of the electro -negative element pres- 

 ent in the binary compound ; and 3, the atomic 

 weights of the constituent elements of the 

 compounds. The color passes, or tends to pass, 

 through the chromatic scale white or color- 

 less, violet, indigo, blue, green, yellow, orange, 

 red, brown, and black either by rise of temper- 

 ature, by increase of the quantity of the electro- 

 negative element in a binary compound, or with 

 increase of the atomic weights of the elements 

 A, B, 0, etc., in the compounds Aa; Ry, Ba? 

 Ry, (jx Ry, etc., in which R is any element or 

 group of elements; while A, B, 0, etc., are 

 elements belonging to the same sub-group of 

 Mendelejeff s classification of the elements. On- 

 ly sixteen exceptions, or four per cent., were 

 met in four hundred and twenty-six cases in 

 which the third of these rules was applied. 



Prof. Frankland, opening a discussion in the 

 British Association on " Chemical Changes in 

 their Relation to Micro- Organisms," thus de- 

 fined the distinction between animal and vege- 

 table organisms : A plant is an organism per- 

 forming synthetic functions, or one in which 

 those functions greatly predominate ; it trans- 

 forms actual into potential energy. An ani- 

 mal is an organism performing analytical func- 

 tions, or one in which these functions greatly 

 predominate ; it transforms potential into act- 

 ual energy. All micro-organisms appear to 

 belong to the second class. There is no break 

 in the continuity of chemical functions between 

 micro-organisms and the higher forms of ani- 

 mal life. It is true, there are apparently sharp 

 distinctions between them. The enormous fe- 

 cundity of micro-organisms and their tremen- 



