several hundred parts per billion of hydrofluoric acid. When interfering ions are known not
Table IV. Results of Fluorine Determinations in 15 Laboratories Supplied with Same Plant Materials
F in Dried Leaves,
Collaborators 1
-
Corn 88 i5 --
2 3
( I
93 81 86 82
1 5 6
7
82
13
14
87
I5
Avrrage
82 81
P.P.11. A4pplr Tea 39 109 35
95
35
101 107
35 3; 44
35 38
98 107
41
94 102 100 113 103
38
101
40 39
to be present, the absorbed fluorine iq titrated directly without being distilled. I n this caSe the air sample is collected in the bubbler described in Figure 3. left. However, when sulfur dioxide or other interfering substances are knon 11 to be present, the absorbed fluorine isteam distilled from a perchloric acid solution, using the apparatus shoivn in Figure 4. A minimum of 4 y of fluorine has to be present in the absorbing qolution, to obtain results n-ith an error not exceeding 10%. Insoluble fluorine compounds n-ere converted into soluble fluoride ion in a relatirelv short time by direct fusion of the plant material with
