6 BULLETIN 143, U. S. DEPARTMENT OF AGRICULTURE. 



Table II. — Proportions in which ingredients were mixed and analyses of melts 



obtained. 





Amount of material used. 



Properties of 

 fusion. 



Analysis of melts. 



Sample No. 



Feld- 

 spar. 



Phos- 

 phatic 



lime- 

 stone. 



Fe 2 3 . 



Mu0 2 . 



P 2 5 

 solu- 

 ble in 

 citric 

 acid. 



Total 



r' 2 o 6 . 



IC 2 

 solu- 

 ble in 

 citric 

 acid. 



Total 

 K 2 0. 



25S 



Per ct. 

 42.8 

 37.5 

 46.8 

 37.5 



Per ct. 

 42.8 

 50.0 

 37.5 

 42.5 



Per ct. 



8.6 

 7.5 

 9.4 

 12.5 



Per ct. 

 5.7 

 5.0 

 6.3 

 7.5 



Slightly viscous.. 

 do." 



Per ct. 

 2.12 



1.50 

 7.22 



5.80 



Per ct. 



9. 76 



11.40 



7.21 



19.13 



Per ct. 

 6.56 

 5.32 

 6.50 

 4.50 



Per ct. 

 6.82 



28 S 



5.68 



33 S 





6.48 



34 S 



do 



5.26 







1 Not determined by analysis, but calculated from the quantity of feldspar added. 



Table II shows that nearly all of the potash present after fusing 

 the various mixtures was soluble in 2 per cent citric acid, but in only 

 one case (33S) was the total phosphoric acid present after ignition 

 soluble in this same medium. 



Further investigation showed that both the quantity and solu- 

 bility of the phosphoric acid remaining in this melt was greatly 

 influenced by the temperature and length of time of heating. In 

 order to test the effect of these two factors on the composition and 

 nature of the melt, this mixture (33S) was heated for various 

 periods of time and at several different temperatures. The melts 

 thus obtained were cooled, ground, and analyzed. The results of 

 these analyses are given in Table III. 



Table III. — Properties and analyses of melts obtained by heating together phos- 

 phatic limestone and, feldspar with small amounts of hematite and manganese 

 dioxide. 



Sample 

 No. 



Tempera- 

 ture of 

 melt. 



Time of 



heating. 



Properties of fusion. 



P 2 6 . 



K 2 0. 



Citric 

 soluble. 



Total. 



Citric 

 soluble. 



Total. 



33 SA 



° C. 

 1,200 

 1,400 

 1,400 

 1,400 



H. m. 

 20 



40 



1 40 



4 40 





Per cent. 

 1.82 

 7.22 

 2.50 

 1.20 



P. ct. 

 8.50 

 7.21 

 3.76 



2.S8 



Per cent. 

 5.98 

 6.50 

 Lost. 

 Not deter- 

 mined. 



Per cent. 



6.76 



33 SB 





6.48 



33 SC 



33 SD 



Less liquid 



5.48 

 Not deter- 







mined. 



It is shown in Table III that when the mixture was heated to 

 1,200° C. for about 20 minutes the fusion was not complete, and only 

 a little more than 21 per cent of the total phosphoric acid present was 

 citric soluble; over 88 per cent of the potash, however, was soluble 

 in the same medium. Upon raising the temperature to 1,400° C. and 

 maintaining it there for 20 minutes the fusion became quite fluid, 

 and, although small amounts of potash and phosphoric acid were 

 lost through volatilization, the remainder of these ingredients was 



