Tli A N.S ACTIONS OF SECTION' B. 



661 



tbeuiy 



tlie active spirils in contincnliil chfinistrv. In our own oounlry, Ciraliam, wIioho 

 nu'iniirable luHcarclies on the phospliati'.s had enabled Liebiir to i'ound liis theory of 

 polybasic acidfi, was workin;r and lecturiiii; at University Collej^o, London ; and 

 Williaiuson. imbued with the new doctriiirs and views of tlio twin French cheniis^ts, 

 !;,ul ju.<t been appointed to tlie cliair of ])ractical chemistry in the same coIie<re, 

 v:U'iuit by tlie death of poor Fownes. At the same time, Ilofmann, in •whom 

 Liebiu' found a spirit as enthusiastic in the cause of seientitic progress as his own, 

 liriiifrinp- to I'lnjrland a {rood share of the Giessen iire, founded the most successful 

 school uf chemistry which this country has yet s:'en. 



At the EdinburLih meetinjx of tliis Association in 1850, Williamson reail a 

 paper on 'Itesults of a Jiescarcb on .l^therilication,' which included not only a 

 Nitisfactory solution of an interesting and hithrrto unexplained problem, but was 

 destined to exert a most important influence on the develo])ment of our theoretical 

 views. Fin- he proved, contraiy to tlu' then iirevailing ideas, that ether contains 

 twice as much cai'bou as alcoluil, and that it is not formed from the latter by a 

 mere si'pavaliiin nf tlie eli'iiients ot water, but by an exchange f)f hydrogen for 

 othyl.and tiiis fact being in accordancf with .\vo:Jradro"s law of molecular volumes, 

 could i>nly be represented by regarding the molecule of water as containing two 

 atoms of hydrogen to one of oxygen, one of the former being replaced by one of 

 etliyl to form alcohol, and the two of hydrogen by two of ethyl to form ether. 

 Then Williamson introduced tiie type of water (subsequently adojited byClerliardt) 

 into organic chemistry, and extended oiiv views of the analogies between alcobols 

 and acids, by pointing out tliat these latter are also referable to the water-type, 

 predicting that bodies bearing the same relations to the ordinary acids as the ethers 

 do to the alcoliols must exist, a jirediction shortly afterwards ( lSo2) verifieil by 

 Gerhardt's discovery of the anhydrides. (Jthor results followed in rapid succession, 

 ill! tending to knit together tlie framework of modern theoretical chemistry. Of 

 these the most important was the ado^ition ol' condensed types, of com])onnds 

 constructed on the type of two and three molecules of water, with which the 

 names of Williamson and Odling are connected, culminating in the researches 

 ofBrodie on the higher alcohols, of I'.ertlielot on glycerine, and of Wurtz on the 

 diljasic alcohols or glycols; wliilst, in another direction, the researches of Ilofmann 

 on the compound amines and amides opened out an entirely new field, showing 

 that either a part or tlie whole of the hydrogen in ammonia can be replaced by 

 other elements or elementary grou])S without the type losing its characteristic 

 properties. 



Again, in 1852, we note the first germs of a theory which was destined to play 

 an all-iinpcutant part in tiie progress of the science, viz., the doctrine of valency or 

 .itomicity, and to Frankland it is that we owe this new departure. .Singularly 

 enough, whilst considering the .symmetry of construction visible amongst the inor- 

 ganic compounds of nitrogen, phosphorus, arsenic, and antimony, and whilst putting 

 forward the fact that the combining power of the attracting element is always 

 satisfied by the same number of atoms, he does not point out the characteristic 

 tetrad nature of carbon ; and it was not until 1S58 that Couper initiated, and 

 Jvekule, in the same year, thoroughly established the doctrine of the linking of the 

 tetrad carbon atoms, a doctrine to which, more than to any other, is due the extra- 

 ordinary progress which organic chemistry has made during the last twenty years, 

 a progress so vast, that it is already found impossible for one individual, even 

 though he devote his whole time and energies to the task, to master all the details, 

 or make himself at home with the increasing mass of new facts which the busy 

 workers in this field are daily bringing forth. 



The subject of the \ii. .:ncy of the elements is one which, since the year above 

 referred to, has given chemists much food for discussion, as well as opportunity for 

 experimental work. ]?ut whether we range luirselves with Kekult?, who supports 

 the unalterable character of the valency of each element, or with Frankland, who 

 insists on its variability, it is now clear to most chemists that the hard and fast lines 

 upon which this theory was supposed to stand cannot be held to be secure. For if 

 the progress of investigation has shown that it is impossible in many instances to 

 »thjc one valency to an element which forms a large number of difl'erent compounda, 



