V O L U M E 2 3 , NO. 7, J U L Y 1 9 5 1 __
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Tal)le 11.
Silica Assay of Liquid Samples h) lIodified Procedure tiasil”
Ludorb
L b SiO2, acidiiuetric OiC SiOz, grabimetnc
” ‘1
975
10 7 1 0 2 20 4 + n 0 I’otasnium silicate solution, Pliiladel~~liia Quartz (‘olloidal silica suspension, nil Pont.
17 G * O L 17 6 1 0n CU.
. \ I I :wid-retaining gritty t~vsitluc~ i v w again encountrrd, arid it :ippcwi:d to tie mow troul)lrwnw with hydrochloric acid uwd i n p1xc.c~of the sulfuric. 3vid. T h r amounts of sodium Huoridts nntl hydrofluoric mid do riot m t r r into coniputationa: rough nir~:iwrementsuffices. Tliv modified procedure affords two adv:intagea: no hydrofluoric acid rwgerit is handlrd. and :I singlr titntiort per saniplr suffices, aside from the alkali detf,rmiii:itioi1.
T o a j-graiii wiglied saniple in a plastic dish werv addtd 10 of water, 0.1 ml. of 0.1% methyl orange, and 5 grams of silica (M~lliric~krodt~ bulky). This mixture was titrated with 7 .I7sulfuric acid to a pink color, with thorough Ptirring as thr: end point approached. 111 equivalentr, the amount of fluoride present equals 1.5 times the timount of acid used. The sodium fluoride reagent ass:tyed 99.4 * 0.5% N a F by this acidimetric method. A sample of it \
