Formalin is an aqueous solution of formaldehyde, which generally contains 37 ~ 40% formaldehyde. Formalin is a colorless liquid with a strong pungent smell, with a boiling point of 96℃ and a specific gravity of1.081~1.086. It is weakly acidic, toxic and corrosive.
Formalin can effectively kill bacterial propagules and spores (such as anthrax spores), and can also kill drug-resistant Mycobacterium tuberculosis and viruses. It is mostly used for fumigation and disinfection of livestock and poultry sheds, warehouses, oozing rooms, furs, clothes and utensils, and anti-corrosion of specimens and corpses.
Formalin and specimen making
If formalin is used as preservation solution, the concentration is 5%- 10%, and 15% can be used in some cases. The specific concentration depends on the size of the specimen. In principle, the concentration of small specimens is small and the concentration of large specimens is high. However, the commonly used preservation solution is almost the same as the fixed solution, mainly formalin, alcohol, glycerol and various mixed solutions made of these drugs in proportion.
Formalin as preservation solution has good effect and low price, and can be used in large quantities. The disadvantage is that paraformaldehyde is often formed during storage, which makes the immersion liquid turbid and affects observation. Therefore, in the process of preservation, a new solution should be replaced once a year.
Refer to the above content: Baidu Encyclopedia-Formalin