Bouin solution is a compound fixative

Fixation (histology)

In the fields of histology, pathology, and cell biology, fixation is a chemical process by which biological tissues are preserved from decay, thereby preventing autolysis or putrefaction...

 used in histology

Histology

Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...

. It is composed of picric acid

Picric acid

Picric acid is the chemical compound formally called 2,4,6-trinitrophenol . This yellow crystalline solid is one of the most acidic phenols. Like other highly nitrated compounds such as TNT, picric acid is an explosive...

, acetic acid

Acetic acid

Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

 and formaldehyde

Formaldehyde

Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

 in an aqueous solution. It is especially good for gastrointestinal tract biopsies because this fixative allows crisper and better nuclear

Cell nucleus

In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...

 staining than 10% neutral-buffered formalin. It is not a good fixative when tissue ultrastructure

Ultrastructure

Ultrastructure is the detailed structure of a biological specimen, such as a cell, tissue, or organ, that can be observed by electron microscopy...

 must be preserved for electron microscopy

Electron microscope

An electron microscope is a type of microscope that uses a beam of electrons to illuminate the specimen and produce a magnified image. Electron microscopes have a greater resolving power than a light-powered optical microscope, because electrons have wavelengths about 100,000 times shorter than...

. However, it is a good fixative when tissue structure with a soft and delicate texture must be preserved. Formalin-fixed tissue is normally mordant

Mordant

A mordant is a substance used to set dyes on fabrics or tissue sections by forming a coordination complex with the dye which then attaches to the fabric or tissue. It may be used for dyeing fabrics, or for intensifying stains in cell or tissue preparations. The term mordant comes from the Latin...

ed with Bouin solution for better staining results in the trichrome stain

Trichrome stain

A trichrome stain is a stain including three colored components. See trichrome article for more information.Types include:* Gömöri trichrome stain* Lillie's trichrome* Masson's trichrome stain...

s. The acetic acid in this fixative lyses

Lysis

Lysis refers to the breaking down of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a "lysate"....

 red blood cell

Red blood cell

Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...

s and dissolves small iron and calcium deposits in tissue. A variant in which the acetic acid is replaced with formic acid

Formic acid

Formic acid is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, formica, referring to its early...

 can be used for both fixation of tissue and decalcification.

The effects of the three chemicals in Bouin solution balance each other. Formalin causes cytoplasm to become basophilic but this effect is balanced by the effect of the picric acid. This results in excellent nuclear and cytoplasmic H&E stain

H&E stain

H&E stain, HE stain or hematoxylin and eosin stain is a popular staining method in histology. It is the most widely used stain in medical diagnosis; for example when a pathologist looks at a biopsy of a suspected cancer, the histological section is likely to be stained with H&E and termed H&E...

ing. The tissue hardening effect of formalin is balanced by the soft tissue fixation of picric acid. The tissue swelling effect of acetic acid is balanced by the tissue shrinking effect of picric acid.

When using Bouin solution, several potential problems can arise. Due to the formalin in the solution, formalin pigment may be present when viewing tissue sections under the microscope. Wet tissue should be fixed in Bouin solution for less than 24 hours. Excess picric acid should be washed out of tissue using several alcohol and water solutions or staining quality may deteriorate over time. Wet tissue fixed in Bouin solution should be stored in an alcohol and water solution rather than Bouin solution. Since Bouin solution contains formaldehyde, picric acid and acetic acid, appropriate safety precautions for these substances should be taken and regulations followed.

Gendre Solution

Gendre solution is an alcoholic version of Bouin solution. An alcoholic solution saturated with picric acid is used instead of an aqueous solution saturated with picric acid when making this solution. This solution is useful when glycogen

Glycogen

Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...

 and other carbohydrate

Carbohydrate

A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

s must be preserved in tissue.

Hollande Solution

Hollande solution is a version of Bouin solution that contains copper acetate

Copper(II) acetate

Copper acetate, also referred to as cupric acetate, is the chemical compound with the formula Cu2 where OAc- is acetate . The hydrated derivative, which contains one molecule of water for each Cu atom, is available commercially. Anhydrous Cu2 is a dark green crystalline solid, whereas Cu22 is...

. The copper acetate stabilizes red blood cell membranes and the granules

Granule (cell biology)

In cell biology, a granule is a small particle. It can be any structure barely visible by light microscopy. The term is most often used to describe a secretory vesicle.-Leukocytes:...

 of eosinophil

Eosinophil granulocyte

Eosinophil granulocytes, usually called eosinophils or eosinophiles , are white blood cells that are one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Along with mast cells, they also control mechanisms associated with...

s and endocrine

Endocrine system

In physiology, the endocrine system is a system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body. The endocrine system is in contrast to the exocrine system, which secretes its chemicals using ducts. It derives from the Greek words "endo"...

cells so that there is less lysis of these cell components than occurs in regular Bouin solution.