40 
this type of soil, as shown in Table XIV, can hardly be said to sup- 
port this theory. 
Table XIV. — Partial analysis of titanium soils. 
SoU No. 
Titanium 
oxid 
(Ti0 2 ). 
Phos- 
phoric 
acid 
soluble 
in hydro- 
chloric 
acid. 
Total 
phos- 
phoric 
acid. 
Soil No. 
Titanium 
oxid 
(TiO»). 
Phos- 
phoric 
acid 
soluble 
in hydro- 
chloric 
acid. 
Total 
phos- 
phoric 
acid. 
33 
Per cent. 
21.90 
28. G4 
27.49 
18.90 
Per cent. 
0.04 
.05 
.09 
.07 
Per cent. 
0.22 
.56 
.34 
.08 
165 
Per cent. 
20.62 
18.84 
20.02 
34.16 
Per cent. 
0.04 
.11 
.11 
.04 
Per cent. 
0.17 
72 
174 
.50 
113 
175 
.27 
164 
199 
.35 
Titanium and total phosphoric acid were determined by fusion 
with sodium carbonate. 
The above figures indicate the insolubility of titanium phosphate, 
but also show the low phosphate content of this type of soil. The 
average phosphate content of Hawaiian soils is about 0.5 per cent 
P 2 5 , while the maximum is 2.32 per cent (determined with hydro- 
chloric acid of specific gravity 1.115), and the maximum absolute 
phosphate content as determined by fusion with sodium carbonate is 
3.50 per cent. It appears, therefore, that the major part of the 
phosphoric acid combined with the titanium in the lava rock remains 
as such in the soil and represents the chemically combined insoluble 
phosphate, but owing to the inert properties of the titanium as com- 
pared with the other elements present in the soil, it may be considered 
to be inactive toward other phosphates already present or any which 
may be added as fertilizers. 
SUMMARY. 
(1) Hydrochloric acid of official strength does not dissolve all of 
the phosphoric acid of Hawaiian soils. To determine the total 
phosphate content, it is necessary to fuse the soil with sodium car- 
bonate. 
(2) Fifth-normal nitric acid has very little solvent action upon the 
phosphate in the soils, indicating the absence of appreciable quantities 
of calcium phosphate. 
(3) One per cent citric acid has a much stronger solvent action than 
fifth-normal nitric acid. 
(4) Of the weaker solvents, 1 per cent sodium hydroxid is the 
strongest, due to its action on the iron and aluminum phosphates. 
(5) The fertilizer (phosphate) requirement of the soil is not meas- 
ured by solubility in water or fifth-normal nitric acid, but it may be 
indicated by the solubility in citric acid. 
