270 



Domestic Science 



use, it is least affected by the action of steam and pure 

 water. 



The nature of the substances to be found dissolved 

 in a sample of ordinary water will receive full treatment 

 in the section of Part II dealing with the domestic uses 

 of water. 



187. On evaporating the various samples of water 

 as above, the residues will have been observed as 

 consisting of masses of indeterminate shape, the separate 

 particles of which each is made up being indistinguish- 

 able from one another. By stopping the heating before 

 dryness is reached it is possible to obtain larger 



.87. 



particles in many cases, the shapes of these being 

 definite, and the substance previously held in solution 

 may frequently be recognised by examination of the 

 form of the separate particles deposited on partial 

 evaporation. 



Those substances which are soluble in water are 

 not all dissolved to the same extent by equal quantities 

 of water. Further, the degree of solubility of any given 

 substance is found to depend upon the temperature of 

 the solvent in some cases to a very considerable extent. 



