606 KEPORT— 1897. 



General Conditions of SolnbilHij. 



1. Substances dissolve each other better the more closely they resemble each 

 other in structure. 



*^* Elements dissolve elements, e.g., Pd in H ; Fe. ?In, Xi, and Al in C ; U, Cr, 

 Ni, V, and W in Fe ; O in Ag, &c. 



Organic substances, like paraifins, containing only C and H, and bodies like- 

 sulphides, free from O, are insoluble in H„0. 



The richer they are in O the more soluble thej^ are in water, e.g., the sulphates. 



Simple bodies dissolve in water, complex bodies in the complex alcohol, benzene, 

 and ether (Belonbex). 



2. In most cases where there is an imitative valency there is like solubility, as 

 AgCl, HgCl, TlCl, CuCl, and AuCl. 



.^. The presence of a common ion reduces solubility. 



4. Solubility generally increases with temperature, and decreases with atomic 

 volume. 



By making use of the tinetic theory of solutions under the head of equilibrium 

 when the study of gases is entered upon, evaporation, diifusion, vapour and osmotic 

 pressure, solution pressure, dissociation, tension, and ionisation may be treated 

 together most advantageously. Clearer ideas are obtained, time is greatly econo- 

 mised, and living interest is added to the subject. Where chemistrj' is taken up 

 .subsequently to a course in experimental physics, or concurrently, the two courses 

 may be made to supplement each other. In the descriptions of a family and the 

 tabulation of value.s, the same principle of classification may be extended, and 

 graphical curves will prove abundantly useful. Dr. M. M. Pattisou Muir's articles in 

 ' Watts's Dictionary ' on the groups of elements are fine examples of what I moan, 

 and my plea is for a larger use of this method in elementary classes. 



II. Simpler Apparatus for more fruitful Research Methods. — The substitution 

 of plaster tablets for charcoal, as a blowpipe support, has made possible for elemen- 

 tary and high schools a clean and cheap method for studying a wide range of 

 chemical changes, without gas pipes and Bunsen burners, water pipes and pneu- 

 matic troughs, rubber and glass tubing, stills, retorts or sinks, gas generators, or 

 hoods. These need be at the hand of the teacher only. On an ordinary school 

 desk, with a two-cent blowpipe lamp as shown upon the table, a blowpipe, 

 some paraffin wax for fuel, three or four ounce and one half-ounce bottles for re- 

 agents, and a supply of tablets, all of which can be kept in a box the size of an 

 ordinary crayon box, experiments can be made testing the fusibility, volatility, 

 oxidisabilitj', and reducibility of the metals. The oxides, sulphides, chlorides, 

 bromides, and iodides may be formed, and their colours and volatility and solubility 

 noted. 



The effect of coloured ions in solutions at high temperatures can be observed iu 

 borax and meta-phosphoric glasses without any expenditure for platinum wire. 

 The quantity of chemical material needed is comparatively a negligible quantity. 

 Within three minutes after a class has entered the laboratory, they have reached 

 results and are recording their observations. In no other form of laboratory 

 work do the compelled acts of judgment follow each other so rapidly. Research 

 methods may be rigorously followed. 



The following problems may be illustrated and studied by means of simple 

 manipulations of this meagre apparatus : The changes which take place in a 

 burning match and the products of combustion ; the effect of mass action on 

 chemical affinity ; the energy changes which take place in fusion and volatilisa- 

 tion, and the effect of cold surfaces on the precipitation of sublimates ; and the 

 conditions of equilibrium between layers of heated gases, besides the formation of 

 a very large number of compounds and exhibition of their properties. All results 

 reached by the dry way should be correlated with analogous results reached in 

 the wet way and the corresponding equations written. 



