20 UNIVERSITY OF COLORADO 



crucible, replace the cover and place in the muffle until the ash 

 turns white, showing the carbon to be completely burned off. Re- 

 move, cool, and weigh. The difference between this weight and 

 the last x 100 = ^ fixed carbon; what remains is ash, which x 100= 

 $ ash. 



Coke. — Essentially the same method as for coal. Coke ash 

 is, however, analyzed for silica, iron, alumina, and lime, as follows: 



Burn about 5 grams of coke in the muffle in order to have a 

 sufficient amount of ash. Pulverize about \ gram finely in an 

 agate mortar, and place in a crucible with about 3 grams of fusion 

 mixture and mix thoroughly; cover with about a gram more of the 

 fusion mixture and fuse in the muffle. Place the crucible, when 

 cool, in a casserole of hot water and boil until the fusion is dis- 

 solved. Cover the casserole with a watch glass and add HC1 from 

 a pipette until effervescence ceases and the solution is acid. Evap- 

 orate to dryness, dissolve the residue in 20 cc. HC1 and 50 cc. boil- 

 ing water. Boil, filter, wash, ignite, and weigh silica. 



Boil the filtrate, and while boiling add ammonia in slight ex- 

 cess, boil, and filter out the ppt. of ferric and aluminic hydrox- 

 ides (containing all the phosphoric acid which, in lead smelters, can 

 usually be neglected), and wash three to four times with boiling 

 water. The filtrate is now boiled, ammonium oxalate is added, 

 the lime thus ppt. being allowed to settle. While the cal- 

 cium oxalate is settling, the ppt. of ferric and aluminic 

 hydroxides is dissolved in dilute HC1, and poured into a 200 cc. 

 flask and diluted to the mark, then poured into a No. 2 beaker, 

 mixed thoroughly and 100 cc. taken out with a pipette. This is 

 placed in a No. 2 beaker, boiled, reduced with stannous chloride, 

 mercuric chloride is added, and titrated with the bichromate solu- 

 tion for iron. Calculate the iron to ferric oxide and report as such. 



'Wash the remainder from the 200 cc. flask into another beaker, 

 and rinse the pipette in it. Place this beaker on the hot plate, 

 and, when the contents are boiling, remove from the heat, add a 

 slight excess of ammonia, again boil, allow to settle, filter, wash, 

 ignite, and weigh as Fe 2 3 +Al 2 3 +P 2 5 , subtract the weights of 

 Fe 2 3 +P 2 5 previously found, and the remainder is A1 2 3 . It must 

 not be overlooked that these weights represent only one-half the 

 amount of substance originally taken, so that the weights must 

 be doubled to obtain the correct amount. The calcium oxalate, 



