6 BULLETIN 143, U. S. DEPARTMENT OF AGEICULTUEE. 
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 . 
P2O5 
solu- 
ble in 
citric 
acid. 
Total 
P2O5. 
K 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 
Perct. 
6.56 
5.32 
6.50 
4.50 
Per ct. 
6.82 
28 S 
5.68 
33 S 
6.48 
34S 
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 ph.os- 
pliatic limestone and feldspar with small amounts of hematite and manganese 
dioxide. 
Sample 
No. 
Tempera- 
ture of 
melt. 
Time of 
beating. 
Properties of fusion. 
P2O5. 
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 
Viscous 
Per cent. 
1.82 
7.22 
2.50 
1.20 
P.ct. 
8.50 
7.21 
3.76 
2.88 
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 
