A toilet rim block is a substance in the shape of a block that is used in

flush toilet A flush toilet (also known as a flushing toilet, water closet (WC) – see also toilet names) is a toilet that disposes of human waste (principally urine and feces) by using the force of water to ''flush'' it through a drainpipe to another loca ...

s, which slowly dissolves in water. The blocks usually come in a small holder that is attached over the rim of a toilet and hangs down into the bowl, so as the toilet gets flushed, the water passes through the holder coming into contact with the block. With "liquid rims", however, liquid is held in a small bottle above—and connected to—the holder that slowly releases into the bottom of the holder (which is beneath the toilet rim), and so coming into contact with the water when the toilet is flushed. However, the blocks also come ''loose'', for placement directly ''in-cistern'' (and therefore usable with squat toilets that lack the same sort of rim), although these tend to be slightly different in composition, so as to dissolve slower, due to the constant contact with water. These may also contain a

colorant A colourant/colour additive (British spelling) or colorant/color additive (American spelling) is a substance that is added or applied in order to change the colour of a material or surface. Colourants can be used for many purposes including printing ...

(typically blue or green) which shows up in the pan or bowl water.

Composition and action

Toilet rim blocks are marketed as

disinfectant A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than s ...

s and

deodorizer Air fresheners are consumer products that typically emit fragrance and are used in homes or commercial interiors such as restrooms, foyers, hallways, vestibules and other smaller indoor areas, as well as larger areas such as hotel lobbies, auto ...

s, while allegedly also helping to prevent the buildup of

limescale Limescale is a hard, chalky deposit, consisting mainly of calcium carbonate (CaCO3). It often builds up inside kettles, boilers, and pipework, especially that for hot water. It is also often found as a similar deposit on the inner surfaces of ol ...

in the toilet bowl. The composition of toilet blocks can vary, but they may contain (among other components):

borax Borax is a salt (ionic compound), a hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a basic solution. It is commonly available in powder or granular form ...

(an ingredient of many detergents), hydroxyethylcellulose (a

gelling agent A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still dif ...

), troclosene sodium (a disinfectant), sodium dodecylbenzenesulfonate (a

surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsion#Emulsifiers , ...

), sodium percarbonate (a form of oxygen

bleach Bleach is the generic name for any chemical product that is used industrially or domestically to remove color (whitening) from a fabric or fiber or to clean or to remove stains in a process called bleaching. It often refers specifically, to ...

sodium carbonate Sodium carbonate, , (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield moderately alkaline solutions ...

("washing soda"), and various perfumes like, e.g.,

limonene Limonene is a colorless liquid aliphatic hydrocarbon classified as a cyclic monoterpene, and is the major component in the oil of citrus fruit peels. The -isomer, occurring more commonly in nature as the fragrance of oranges, is a flavoring a ...

, butylphenyl methylpropional, and

linalool Linalool () refers to two enantiomers of a naturally occurring terpene alcohol found in many flowers and spice plants. Linalool has multiple commercial applications, the majority of which are based on its pleasant scent (floral, with a touch of ...

.
/ref> As in the closely related

urinal deodorizer block Urinal deodorizer blocks (commonly known as urinal cakes, urinal cookies, urinal biscuits (piscuits), urinal donuts, toilet lollies, trough lollies, urinal mints, urinal pucks, hockey pucks, toilet pucks, or urinal peons (pee-ons) are small disinf ...

s, some of the ingredients have irritating effects when applied to skin, eyes, or when swallowed. Their ecotoxicity is rated to be harmful to aquatic organisms and these chemicals may have long-term adverse effects for an aquatic environment.

References

{{reflist Hygiene Cleaning products Toilets

Composition and action

See also

References