Bromoform

Bromoform (CHBr₃) is a pale yellowish liquid with a sweet odor similar to chloroform, a halomethane or haloform. Its refractive index is 1.595 (20 °C, D). Small amounts are formed naturally by plants in the ocean. It is somewhat soluble in water and readily evaporates into the air. Most of the bromoform that enters the environment is formed as byproducts when chlorine is added to drinking water to kill bacteria.

Additional recommended knowledge

How to ensure accurate weighing results every day?

Daily Visual Balance Check

Weighing the right way

Bromoform is one of the trihalomethanes closely related with fluoroform, chloroform and iodoform. It is soluble in about 800 parts water and is miscible with alcohol, benzene, chloroform, ether, petroleum ether, acetone, and oils. It's LD₅₀ is 7.2 mmol/kg in mice, or 1.8g/kg.

It can be prepared by the haloform reaction using acetone and sodium hypobromite or by the electrolysis of alcoholic solution of potassium or sodium bromide.

Uses

Only small quantities of bromoform are currently produced industrially in the United States. In the past, it was used as a solvent, sedative and flame retardant, but now it is mainly used as a laboratory reagent.

Due to bromoform's relatively high density, it is commonly used for the separation of minerals. In one application of the technique, two samples can be separated by bromoform in a test tube or equivalent glassware. The top layer which contains the lighter minerals can be removed from the bottom layer which contains the heavier minerals.

This ability of bromoform to support the weight of some solids is explained by the laws of buoyancy. A solid will float in a liquid if its density is less than that of the liquid. Likewise, a solid will sink if its density is more than that of the liquid. If a liquid is to be used to separate minerals according to their densities, it should have a density that is in between that of the minerals. Bromoform has a high density compared to that of other liquids, and so it is ideal for this application. If the density of bromoform is slightly too high, then it can be brought down by mixing it with a small amount of fully miscible liquid of lesser density.

See also

• Haloalkane
• Halomethane
• Trihalomethane
• Bromomethane
• Dibromomethane
• Tetrabromomethane
• Fluoroform
• Chloroform
• Iodoform

References

• Betterton E. A., Arnold R. G., Kuhler R. J., Santo G. A. (June 2005). "Reductive dehalogenation of bromoform in aqueous solution". Environ Health Perspect. 103: 89-91(3). PMID 8565919. Retrieved on 2007-07-03. PDF