What is the similarity between solid solutions ofI. SrCl2 and NaCl ?II.CdCl2 and AgCl ?

Both the solutions show impurity defect. When molten NaCl containing a little amount of SrCl2 is crystallised, some of the sites of Na+ ions are occupied by Sr2+. Each Sr2+ replaces two Na*ions. It occupies the site of only one ion and the other site remains vacant. The cationic vacancies, hence produced are same in number as that of Sr2+ ions. Same case is with the solid solution of CdCl2 and AgCl.