Arsenic

Location:  Group 15, Period 4
Atomic Weight:  74.9216
Coordination Number:  6
Chemical Form in Solution:  H₃AsO₄ and HAsO₂

_{Intended Use: For the calibration of analytical instruments and validation of analytical methods as appropriate.}

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:  Arsenic has no cationic chemistry. It is soluble in HCl, HNO₃,H₃PO₄, H₂SO₄ and HF aqueous matrices water and NH₄OH. It is stable with most inorganic anions (forms arsenate when boiled with chromate) but many cationic metals form the insoluble arsenates under pH neutral conditions. When fluorinated and/or under acidic conditions arsenate formation is typically not a problem at moderate to low concentrations.

Stability:  2-100 ppb levels - stable for months alone or mixed with other elements at equivalent levels - in 1% HNO₃ / LDPE container. 1-10,000 ppm solutions chemically stable for years in 1-5% HNO₃ / LDPE container.

As Containing Samples (Preparation & Solution):  Metal (soluble in 1:1 H₂O / HNO₃); Oxides (the oxide exists in crystalline and amorphous forms where the amorphoric form is more water soluble. The oxides typically dissolve in dilute acidic solutions when boiled); Minerals (one gram of powered sample is fused in a Ni⁰ crucible with 10 grams of a 1:1 mix of K₂CO₃ and KNO₃ and the melt extracted with hot water); Organic Matrices (0.2 to 0.5 grams of the sample are fused with 15 grams of a 1:1 Na₂CO₃ / Na₂O₂ mix in a Ni⁰ crucible. The fuseate is extracted with water and acidified with HNO₃).