Bathtub ring

In addition to the formation of scale or corrosion of metal within boilers, auxiliary equipment is also susceptible to similar damage. Attempts to prevent scale formation within a boiler can lead to makeup line deposits if the treatment chemicals are improperly ehosen. Thus, the addition of normal phosphates to an unsoftened feed water ean eause a dangerous eondition by elogging the makeup line with preeipitated calcium phosphate. Deposits in the form of calcium or magnesium stearate deposits, otherwise known as "bathtub ring" can be readily seen, and are caused by the eombination of ealcium or magnesium with negative ions of soap stearates. 

Tetrasodium etidronate is used as a water softener in soaps to prevent soap scum and bathtub rings by locking up the calcium and magnesium in the water. 

We first write the balanced equation for the formation of bathtub ring. 

A second problem with hard water is that these metals react with soap molecules and form a scum to which bathtub rings, etc., are attributed. Hard water is therefore not the best water to use for efficient soapy water cleaning processes, since the metal-soap precipitation reaction competes with the cleaning action. Water softeners assist with solving this problem too. 

As noted above, the original product design problem was to formulate a cleansing bar that did not leave a bathtub ring. In addition to this primary attribute, however, the product had to be generally recognizable as a high qual-... 

Bathtub rings are made of this white, waxy solid. Since soap does not dissolve in hard water, there are few suds. 

Ca2+(aq) + 2NaC17H350 2(aq) -> Ca(C17H3502)2(s) + 2Na+(aq) As a result, the effectiveness of the soap is reduced. The insoluble salts form a scum on clothing and a grey slimy deposit in sinks and bathtubs "bathtub ring."... 

This is the type of substance responsible for bathtub rings. Before synthetic detergents were introduced for shampoos, some of the scum left over from soap would remain in people s hair after they washed it with soap. People would have to rinse their hair with vinegar to wash out the solid salts left over from the soap. 

Ca(HC03)2 and MglHCOs) - Such salts are converted to insoluble carbonates (boiler scale) when the water is heated and form objectionable precipitates (bathtub ring) with soaps. When hard water is passed through a column packed with a zeolite that has Na ions in its structure, the Ca and Mg ions exchange with the Na ions and are removed from the water phase ... 

A useful application of oxalic acid is the removal of rust (Ee203) from, say, bathtub rings according to the reaction... 

Oxalic acid is sometimes used to remove bathtub rings that consist of rust, or Fc203. 

Oxalic acid (C2H2O4) is a poisonous substance used chiefly as a bleaching and cleansing agent (for example, to remove bathtub rings). Calculate the concentrations of all the species present at equilibrium in a 0.10 M solution. 

Lime soaps Calcium matter which forms as a curd when soap is used in hard water. An example is a bathtub ring. 

Water containing a relatively high concentration of Ca, Mg, and other divalent cations is called hmd water. Although the presence of these ions is generally not a health threat, they can make water unsuitable for some household and industrial uses. For example, these ions react with soap to form an insoluble soap scum, the stuff of bathtub rings. 

Using synthetic detergents is one way to combat the problem of hard water and bathtub ring. Another way is to simply remove the cations responsible for the hard water before they reach the house. You can accomplish this feat through a home water softener (see Figure 17-4). 

Modern shampoos are simple surfactants, such as sodium lauryl sulfate and sodium dodecyl sulfate. Shampoo contains other ingredients, however, that react with the meted ions in hard water to help prevent the soap from precipitating with these metal ions (in other words, to help prevent insoluble precipitates — solids, deposits, bathtub ring — from forming in your hair). 

Biofilm formation at the air-water interface. The bathtub ring often formed at the air-water interface around the sides of the basin is likely to be a biofilm due to microbial activity. This film acts like a trap and is known to concentrate caesium and other radioactive isotopes contained in the basin water. This biofilm should be removed mechanically by wet brushing, using water to hold down any airborne activity. A 35% solution of hydrogen peroxide has proven effective in suppressing microbial activity and could be used to assist in biofilm removal without corrosive attack on aluminium alloys. 

---