12H_{2}O)
in water, and making up to 1 litre. 100 c.c. will contain 0.5 gram of
phosphoric oxide (P_{2}O_{5}), or 0.2183 gram of phosphorus. In making
this solution, transparent crystals only must be used. The uranium
acetate solution is only approximately equivalent to this, so that its
exact standard must be determined.
_Sodic Acetate and Acetic Acid Solution._--It is the same as that
described under _Arsenic_.[111] Use 5 c.c. for each assay.
The following experiments show the effect of variation in the conditions
of the titration:--
~Effect of Varying Temperature.~--The solution should be titrated while
boiling. This is especially necessary for the last few c.c. in order to
get a decided and fixed finishing point.
Temperature 15° C. 30° C. 70° C. 100° C.
"Uranium" required 18.0 c.c. 19.2 c.c. 19.0 c.c. 18.9 c.c.
~Effect of Varying Bulk.~--
Bulk 50.0 c.c. 100.0 c.c. 200.0 c.c. 300.0 c.c.
"Uranium" required 18.8 " 18.9 " 19.0 " 19.3 "
Variation in bulk affects the results; therefore, a constant bulk should
be adhered to.
~Effect of Varying Sodium Acetate and Acetic Acid Solution.~--
Sodium acetate
and acetic
acid solution 0.0 c.c. 1.0 c.c. 5.0 c.c. 10.0 c.c. 20.0 c.c.
"Uranium" required 18.
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