Thorium

Location:  Period 7 (actinoid)
Atomic Weight:  232.0381
Coordination Number:  8
Chemical Form in Solution:  Th(OH)³⁺ and Th(OH)₂²⁺

Storage & Handling:  Keep tightly sealed when not in use. Store and use at 20 ± 4°C. Do not pipet from container. Do not return portions removed for pipetting to container.

Chemical Compatibility:  Soluble in HCl and HNO₃. Avoid H₃PO₄, H₂SO₄, and HF, although solubilities may not be a problem depending upon pH and matrix (i.e. - ThF₄ is soluble in acids). Avoid neutral to basic media. Th⁴⁺ is stable with most metals and inorganic anions forming an insoluble carbonate, oxide, fluoride, oxalate, sulfate, and phosphate in neutral to slightly acidic media.

Stability:  2-100 ppb levels stable for months in 1% HNO₃ / LDPE container. 1-10,000 ppm solutions chemically stable for years in 2-5% HNO₃ / LDPE container.

Th Containing Samples (Preparation & Solution):  Metal (soluble in aqua regia); Oxide (the heated oxide is not soluble in acids except hot conc. H₂SO₄); Ores (Na₂O₂ fusion at 480 ± 20°C for 7 minutes, cool, and treat sintered mass with 50 mL cold water and let stand until disintegrated. The mass is transferred to a beaker and acidified with HCl, with 25 mL excess HCl added. Any residue is collected on a Whatman No. 42 filter, dried and ignited to 1000°C in Pt⁰ crucible and ash treated with H₂SO₄ / HF and fumed. If residue remains, then treat it by peroxide fusion as described above).