Bromoform

Overview
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.

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 bottom layer containing the heavier minerals can be frozen with liquid nitrogen, while the remaining top layer can be poured off, free of the other minerals.

This ability 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 inbetween that of the minerals.