Appendix 235 



the residue with conceDtrated hydrochloric acid, evaporate to dry- 

 ness, treat with dilute hydrochloric acid, filter and wash, determine 

 the potash in the filtrate as in (a). 



{d) Flue dusts. 10 grams are ignited gently to char organic 

 matter, then boiled with 300 c.c. water. Add 10 c.c. concentrated 

 hydrochloric acid slowly so as not to check the boihng ; then boil for 

 a further 10 minutes. Filter into a 500 c.c. flask and raise to boihng 

 point: add powdered barium hydroxide to slight excess, cool, make 

 up to 500 c.c, filter. To 250 c.c. of the filtrate add ammonia and 

 excess of ammonium carbonate, and, while boihng, a little powdered 

 ammonium oxalate. Cool, make up to 500 c.c. and filter. Evaporate 

 50 or 100 c.c. of the filtrate to dryness: heat the residue gently over 

 a low flame to expel ammonium salts, keeping the temperature care- 

 fully below redness. Moisten with concentrated hydrochloric acid, 

 evaporate to dryness, treat with dilute hydrochloric acid, filter, 

 determine the potash as in (a). 



