502 
PACIFIC SCIENCE, Vol. XX, October 1966 
position of the melt with hydrochloric acid 
(Jackson, 1958). Potassium was determined 
by the flame photometer method, using a 
Model 21 Coleman Flame Photometer. Alumi- 
num was analyzed by Chenery’s colorimetric 
method, as modified by Moomaw et al. (1959). 
The entire experiment was repeated 10 times. 
A homogeneity test was conducted using the 
M-value as the criterion (Hartley, 1944). In 
its final form, the M-test involves computing 
ucts from the soil-phosphate systems were con- 
taminated with Al-containing soil particles. 
From the preceding experiments it is clear 
that the active constituent reacting with phos- 
phate in Akaka soil is aluminum rather than 
iron. Recent work on the precipitation of phos- 
phate in acid soils by Taylor et al. (1964) also 
revealed that aluminum hydroxide is the prin- 
cipal reagent in the precipitation of phosphate 
from fertilizers in acid soils. 
M= (n x + n k )log e 
n l s l 2 “b * * * n k s k~ 
n i + ’ • • + n k 
— (nJogeSi 2 — n k log e s k 2 ) 
where there are k samples, n l5 . . . n k , are the 
respective degrees of freedom and s 4 2 , . . . s k 2 
the respective estimates of variance. The ho- 
mogeneity test showed that 3 of the 10 experi- 
ments were not homogeneous with the others 
and therefore they were rejected. Data obtained 
from the 7 remaining experiments were com- 
bined. Analysis of variance with respect to the 
ratios K/P0 4 and A1/P0 4 were carried out. 
The amounts of soil used did not affect signifi- 
cantly the ratios K/P0 4 or A1/P0 4 . 
The possibility of isomorphous substitution 
of iron for aluminum in the reaction product, 
under the conditions of investigation, was also 
examined. Relatively pure crystalline reaction 
products were selected and were ignited over a 
Meker Burner. When ignited, the crystals 
should show a reddish color if iron -substituted 
taranakite is present. This did not occur; upon 
ignition, the iron-containing compounds gave 
hematite. 
The average values of K/P0 4 and A1/P0 4 
obtained from the seven experiments were con- 
sidered to be taken from a representative sam- 
ple because the M-test proved to be nonsignifi- 
cant. The molar ratios of K/P0 4 and A1/P0 4 
for the reaction products were 0.37 and 0.72, 
respectively. Those for the synthesized tarana- 
kite were 0.37 for K/P0 4 and 0.60 for 
A1/P0 4 . These values are very close to the ones 
calculated from the formula of taranakite es- 
tablished by Smith and Brown (1959), which 
is 0.38 for K/P0 4 and 0.63 for A1/P0 4 . The 
molar ratio A1/P0 4 for the reaction products 
is somewhat higher because the reaction prod- 
Characterization of Phospho-reaction Products 
by Optical Methods, Infrared Analysis, and 
Differential Thermal Analysis 
Optical properties of the reaction products 
from the soil-phosphate systems and from syn- 
thesized taranakite were determined. In addi- 
tion to the synthesized taranakite already de- 
scribed, a second synthetic preparation was 
prepared as follows: 10 ml. of 1.5 molar mono- 
potassium phosphate solution was mixed with a 
solution containing 0.25 g aluminum by 
vigorous stirring. The pH of this mixture was 
adjusted to 4.0 with 10% potassium hydroxide. 
The precipitates formed were kept in water at 
50 °C for a period of time. They were then 
filtered, washed with distilled water, and air- 
dried. 
Immersion liquids were used to determine 
refractive indices. Other optical properties were 
studied by using thin sections of minerals 
mounted in Lakeside 70 Transparent Cement. 
When examined under the polarizing micro- 
scope, both the reaction products obtained from 
the soil-phosphate systems and the synthesized 
taranakite were biaxial negative with a very 
small value of 2V. The refractive indices de- 
termined for the phospho-reaction product 
werena = 1.504, n(3 = 1.507, ny = 1.509, and 
ny ■ — na = 0.005. Those for the synthesized 
taranakite were: na = 1.503, n(3 = 1.505 and 
ny = 1.506, ny — na = 0.003. These values 
are in reasonable agreement with those obtained 
by Haseman et al. (1950). The crystals are 
colorless and occur as tiny columnar aggregates. 
The aggregates of crystals tend to grow to- 
gether, perpendicular to each other in pairs, to 
form a twinlike crystal in a rosette pattern, dis- 
playing a pseudohexagonal outline. 
Smith and Brown (1959) re-examined the 
