141 



Gladding method. 



Ii<s..lve \ -rams of tho rock in 30 cc dilute hydrochloric acid (1 to 1), heating just 

 below the boiling point for half an hour. Filter into a 200 cc flask, add a few drops 

 c.f nitric and, and boil to oxidize the iron; cool and dilute to mark. Take 50 cc, con- 

 taining 1 gram, and run into 20 cc of a solution of C. P. caustic potash, made by dis- 

 Bolving -">00 grams of caustic potash free from alumina, in distilled water and diluting 

 to i. in- liter. Digest in water bath at 70 for one hour, stirring occasionally. Let the 

 precipitate settle and filter on a large paper, first decanting the supernatant liquid 

 on th.- paper and finally washing on the precipitate. Wash two or three times with 

 hot water. To the filtrate add 1 gram of ammonium phosphate; acidify with hydro- 

 chloric acid. Add ammonia until a permanent precipitate is formed; add dilute 

 hydrochloric acid, drop by drop, until it is just dissolved. 



Add a mixture of 15 cc neutral ammonium acetate solution and 5 cc acetic acid 

 (30 per cent) and digest for half an hour at 70 C., by which time the precipitation is 

 complete. Filter, washing five or six times with hot ammonium acetate solution 

 (10 per cent), stirring ui> the precipitate with the jet each time. Ignite with a low 

 flame till the paper is charred, increase the heat until the paper is consumed, then 

 bla.-i lor a minute. 



The precipitate is A1PO 4 and its weight multiplied by 0.418 gives the AL>O 3 . Glad- 

 din- determines the iron oxid volumetric-ally by the bichromate method in a solu- 

 tion of the precipitate of iron oxid and calcium phosphate thrown down by the caustic 

 potash, or by the same method in a separate solution of 5 grams of the rock in dilute 

 hloric acid (1 to 1). 



Glaser method. 



nuns of pho-phaio r , M .k thirty minutes in 30 cc concentrated hydrochloric 



acid. Make up to :tm <-.- and filter off 100 cc. Add 25 cc concentrated sulphuric 



arid: -hake ami allow to -tand a few minutes; add 100 cc strong alcohol and cool. 



'i cc with alcohol and allow to stand thirty minutes; filter off 100 cc or 



ram and evaporate in a larje beaker to expel alcohol. 



M-fer i,, a -mall (Jriflin beaker, boil, remove from flame, and make slightly alka- 

 line with ammonia l'."il to neutrality, cool, filter, and wash with boiling ammonium 

 nitrate solution. Burn and weigh, weight divided by 2= oxids of iron and aluminum. 



Proposed modification of acetate method. 



Weigh 2.5 grams of phosphate rock into a 250 re flask; cover with 25 cc of concen- 

 t rated h\drochlorir and: keep just below the boiling point for thirty minutes; dilute 

 and COOl; make up to the mark: filter off 50 cc, equivalent to one-half gram of rock; 

 add a few drops of nitrir arid, to oxidi/e any ferrous iron, and boil. 



Add ammonia until the precipitate formed dissolves slowly on agitation. Then 

 riMil toahout l."> C., neutrali/e, adding dilute ammonia drop by drop until the precipi- 

 tation i- complete < lear up with dilute hydrochloric acid added drop by drop, 

 slowly ami with frequent shaking toward the* last until the solution is clear. Make 

 a solution of ammonium acetate by neutralizing strong ammonia with acetic acid 

 ;. l.oi; to l", <c of this solution add 5 cc of acetic acid, sp. gr. 1.04, in a tall beaker 

 ha\ in- a -apu- ity of about one liter; fill the beakerabout seven-eighths full with hot 

 water, so that the mixture will have a temperature of 70 to75C.; pour the solution of 

 pho-phate in a thin ,-tream into the dilute hot solution of the ammonium acetate, 

 stilling ron-taiitlv. The precipitated phosphates of iron and aluminum are allowed 

 ml alter ben .in ing dear the greater part of the supernatant fluid is siphoned, 

 off, the beaker is filled up again with hot water at about 70, again allowed to settle, 

 and the supernatant fluid is siphoned off. 



The remainder in the beaker is now filtered off on a large, rapid filtering paper 

 (S. & S. black band ashless) washed thoroughly with hot water containing ammonium 

 nitrate, keeping the precipitate on the filter well stirred up with a strong jet from the 

 wash bottle. Ignite at a low temperature, till the paper is charred, increase heat 

 until the paper i> fully consumed, and finally blast for a minute. The weight of the 

 precipitate in centigrams gives the percentage of the mixed oxids. 



It is desired that in the last two methods the percentage of the mixed oxids of iron 

 and alumina be given and also that the oxid of iron be determined separately by any 

 volumetric method preferred by the analyst, always observing the precaution of 

 oxidizing the organic matter to be found in solutions of phosphate rock by digesting 

 with potassium chlorate and boiling off the excess of chlorin previous to the reduction 

 and titration. 



