252-258] INSOLUBLE SUBSTANCES J I 



nous silica is left. Transfer to a porcelain dish, cautiously 

 evaporate to dryness, and ignite gently. Now cover with 

 strong HC1, warm, and dilute with water. The silica will be 

 left in an insoluble form, and may be filtered off. 



252. The solution is then examined for metals by 

 Tables II. and III. (236 and 237), and for acid-radicals by 

 Tables IV. and V. (240-249). 



253. Since HC1 has been added, a portion of the original 

 powder should be boiled with sodium carbonate solution, 

 the solution filtered, and then tested for chloride by adding 

 dilute HNO3 m excess, and afterwards AgN0 3 solution, 

 when a white precipitate of silver chloride will form if 

 chloride is present. 



254. Nitrates are not found in insoluble bodies, as all 

 nitrates are soluble in water. 



255. Since Na and K cannot be tested for in the solu- 

 tion obtained after fusion, owing to the fusion mixture 

 consisting of Na 2 C0 3 and K 2 C0 3 , it is necessary to use a 

 separate portion for the detection of these metals. 



256. The most convenient method is that of Lawrence 

 Smith. Mix the powdered substance with six times its 

 weight of a mixture of one part pure solid AmCl and six parts 

 pure precipitated CaC0 3 . Place in a crucible, and heat to 

 redness for twenty minutes. Allow to cool, boil up with 

 water, and filter. The filtrate will contain the alkalies 

 together with excess of calcium hydroxide. Precipitate the 

 calcium by adding AmHO, Am 2 C0 3 , and a few drops of 

 Am 2 C 2 0, solution ; filter, evaporate to dryness, and 

 ignite. 



257. Dissolve in a very small quantity of water ; test 

 for sodium by holding a little of the solution in the Bunsen 

 flame on a platinum wire, when the golden flame coloration 

 will be seen if Na is present. 



258. Potassium may be detected by viewing the flame 

 through an indigo prism or cobalt glass, when the crimson 



