Show How to Make Invisible Ink A solution lon of ot equal parts of ot of ot Copper opper and sal s1 ammoniac In water writes rites J Greig In the Boys Boy's OS Own Paper Paper Pa per gives Ilves an Invisible writing which appears In yellow characters when heat is applied Writing done with sulphate of ot copper dissolved alone alono comes forth In a n fine blue when held hei held over the tile mouth of an ammonia bottle A solution of sulphate of Iron when used for writing may be deve developed black by l infusion of ot oak galls or b by a 8 solution of tannin by applying Instead a 3 solution of ot yellow ellow of potash pot ash It Is brought out In blue The solution of ot of potash for writing can cun of course COUlse be developed In bl blue e b by sing reversing the pr process cess but by using solution of sul suI sulphate phate plate of copper to 10 develop the writing writing writ writ- ing ts red |