Ionic strength and ion ratio effects on the single crystal growth of calcium oxalate monohydrate

Conference · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6476987

DeLong, J D; Briedis, D M

Single crystal growth rates of calcium oxalate monohydrate, CaC/sub 2/O/sub 4/ . H/sub 2/O, were measured as a function of ionic strength and of calcium to oxalate free ion ratio. The photomicroscopic technique was used which allowed measurement of the growth rates of individual faces of single crystals. The amounts of reagents required to maintain a constant relative supersaturation of 3.7 for all experiments were determined using an iterative computer algorithm which allowed the use of various background electrolytes, ionic strength, and free ion ratios. For a range of ionic strengths of I = .0024 to 0.5 for each of the background electrolytes KCl, LiCl, and KClO/sub 4/, and a free ion ratio (Ca/sup 2+/)/(C/sub 2/O/sub 4//sup 2-/) = 1, facial growth rate showed a steady increase with ionic strength towards an asymptotic maximum. The curves of growth rate, R, versus ionic strength followed approximately the form R = k I/sup n/ with 0 < n < 1, suggesting a mechanism of growth enhancement with increasing ionic strength by compression of the electrical double layer at the crystal/solution interface. For a range of free ion ratios (Ca/sup 2+/)/(C/sub 2/O/sub 4//sup 2-/) = 0.01 to 100 and an ionic strength of I = 0.15 M, the observed growth rate showed a maximum at equimolar free ion conditions, with decreasing growth rates observed at lower and higher ion ratios. This growth rate maximum was not apparent under conditions with no added background electrolyte. These results indicate that relative supersaturation as usually used for crystal growth may not be the complete or appropriate driving force for describing electrolyte crystal growth.

• OSTI ID: 6476987
• Report Number(s): CONF-871113-
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ALGORITHMS
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CARBOXYLIC ACID SALTS
CHLORIDES
CHLORINE COMPOUNDS
COMPUTER CALCULATIONS
CRYSTAL GROWTH
CRYSTAL GROWTH METHODS
CRYSTALLOGRAPHY
CRYSTALS
ELECTROLYTES
HALIDES
HALOGEN COMPOUNDS
HYDRATES
LITHIUM CHLORIDES
LITHIUM COMPOUNDS
LITHIUM HALIDES
MATHEMATICAL LOGIC
MICROSCOPY
MONOCRYSTALS
OXALATES
POTASSIUM CHLORIDES
POTASSIUM COMPOUNDS
SATURATION
STRUCTURAL CHEMICAL ANALYSIS
SUPERSATURATION