I N D U S T R I A L A N D ENGINEERIXG CHEMISTRY
November. 1928
1198
Solubilities of Some Inorganic Fluorides in Water at 25” C.’ R. H. Carter I\SZCTICIDEDIVISION.BVREAU OF CHEMISTRY A S D
2RIXG the past few years there has been 3 marked increase in the use of fluorine compounds for many purposes, especially as insecticides against agricultural insect pests of several kinds. When used as agricultural insecticides, compounds of too great solubility not only cause burning of the foliage of tender plants but are also too quickly lost by solution in the rain and den-. On the other hand, the compounds of extremely low solubility are without sufficient toxic action. The problem therefore resolves itself into obtaining compounds which are sufficiently soluble to have the desired toxicity to insect organisms, and yet are not soluble enough to cause burning of plant foliage or to be quickly lost by being washed off by rain and dew. The solubilities of the inorganic fluorides a t different temperatures have been determined by several investigators, with considerable variations in their results. A compilation of previous determinations is given in Table I. It was therefore deemed advisable to determine the solubilities of the more common inorganic fluorides a t one temperature in order to hare a basis for comparison. hlaTERr.lLs-Severa1 inorganic fluorides were made in the laboratory by methods mentioned in the literature and carefully purified until a purity of at least 99 per cent mas obtained.
D‘
Table I-Solubilities COMPOUND
of Fluorides Reported by Other Investigators
FORMULA SOLUBILITY TEMP. Grams per 100 CC. soln.
Calcium fluoride Magnesium fluoride Strontium fluoride Cryolite (synthetic)
CaFz MgFz SrF2 NasAlFe
0.0087 0.0117 0,041
Lead fluoride
PbF:
0,0641
Cupric fluoride
CuF?
Slightly soluble
Ferric fluoride
FeFs
Slightly soluble 0.161
REFEREXCE
C. 18 Kohlrausch 2. pizysik. 18 Chem., 64, 129 (1908). . , Treadwell and Kohl, Helo. Chim. Acta, 9, 470 (1926). 18 Kohlrausch, 2. p h y s i k . Chem., 64. 129 (1908). . . Poulenc, A n n . ’ chim. phys., [7] 2, 68 (1S94), Moissan. Ibid., [GI 24, 347 - . . i~l R Q l i
Van Nostrand Chemical Annual 2 5 Kohlrausch, Z. p h j s i f ? . Chem., 64, 168 (1906). 18 Mylius, Funk, Ber., 30, 1718 (1897).
Uarium fluoride
BaFz
Lithium fluoride
LiF
Manganous fluoride
hInF2
Insoluble
..
.iluminum fluoride
AlFo
Soluble
..
Cadmium fluoride
CdF?
4.36
25
Cobaltous fluoride
CoFz
Zinc fluoride
Slightly soluble
ZnFz.41%0
0.27
1.6
.. 1s
1-ickelous fluoride
SiFl
0.02
..
Sodium fluoride
SaF
4.3
1s
L 4 ~ ~ ~ 4 ~electrically ~ % ~ heated, ~ ~ - automatically h regulated water thermostat was used for maintaining constant temperature of the solutions. As 25’ C. was selected as representing approximately the average temperature of field conditions, the thermostat was kept a t this temperature * 0.1”. PROCEDURE-Excess amounts of the fluorides were mixed with distilled water and placed in the thermostat and shaken from time to time to insure a sat,urated solution. These 1 Presented a s a p a r t of the Insecticide Symposium before t h e Division of Agricultural a n d Food Chemistry a t t h e 75th Meeting of t h e -4merican Chemical Society, St. Louis, AIo,,April 16 t o 19, 1928.
S O I L S , \vASHINGTOX,
D . C.
qolution mixtures were kept in the theriiiostat foi 3 day* or longer to insure saturation and also to allow the aubpended and colloidal matter to settle so that clear samples could be taken. Samples were pipetted, filtered if necessary, and the amount in solution was determined by evaporation of the water or by analytical methods. When the solutions were evaporated analytical methods were employed to check the composition of the residues. Particular care was used in all cases to obtain saturated solutions free from suspended and colloidal material. The p H value of these saturated solutions was determined by the use of a La Xotte set of indicators and color standards. The results arranged in the order of increasing solubility are given in Table 11. Table 11-Solubilities COXPOUKD
Calcium fluoride Magnesium fluoride Strontium fluoride Cryolite (synthetic) Lead fluoride Cupric fluoride Ferric fluoride Barium fluoride Lithium fluoride 1Ianganous rluoridc .\luminum fluoride
