Non-carbonate hardness

Many analyses quote total hardness. Some give temporary hardness (or carbonate hardness) and permanent hardness (or non-carbonate hardness), usually in consistent units so that the values can be added together to give the total hardness. The total hardness is actually the quantity of calcium (Ca) - - magnesium (Mg) in the water. If the total is not given directly, the values given for these two constituents must be added, after conversion to mg/1 as CaC03 if necessary. 

This hardness, which can be removed by heating, is called temporary or carbonate hardness. Temporary hardness is derived from contact with carbonate (limestone and dolomite). Hardness which cannot be removed by boiling is called permanent or non-carbonate hardness and it is due to anions, such as chloride, nitrate, sulfate and silicate. This hardness does not contribute to scale formation. Contact with gypsum would result in permanent hardness. Calcium hardness is that due to Ca only, while magnesium hardness is due to Mg only. Magnesium hardness can be calculated from a determination of total and calcium hardness ... 

Hardness caused by other calcium and magnesium salts is called non-carbonate hardness (formerly permanent hardness). It cannot be removed by boiling. 

Non-carbonate hardness is generally reduced by the lime-soda process, which involves treatment with slaked lime and soda ash (28.7, 28.8). The magnesium is precipitated by the lime as the hydroxide at pH 9 to 10. The co-produced calcium salt, together with other calcium salts originally present, reacts with the soda ash to form a calcium carbonate precipitate. The precipitates are generally removed as sludges by settling and/or filtration. 

Lime-soda ash softening, followed by settling or filtration, can be used to remove suspended solids and non-carbonate hardness, and to reduce the carbonate hardness to the required level. 

Hardness approximates to the concentration of calcium and magnesium salts in water. Total hardness is the sum of carbonate and non-carbonate hardness. It may be expressed as degrees of hardness, millimoles per litre (expressed as calcium equivalent), or as parts per million of CaCOs equivalent. 

Non-carbonate hardness is hardness in water caused mainly by calcium and magnesium compounds other than the bicarbonates. 

NON-CARBONATED HARDNESS - Hardness in water caused by chlorides, sulfates, and nitrates of calcium and magnesium. 

Non-carbonate hardness The amount of hardness that is in excess of carbonate hardness, i.e. hardness in water caused by chlorides, sulphates and nitrates of calcium and magnesium (formerly called permanent hardness ). See Hardness. 

So-called total hardness So-called carbonate hardness So-called non-carbonate hardness... 

In order to relate the hardness to the chemical species, it is customary to refer the part of the total hardness that is chemically equivalent to the bicarbonate plus carbonate alkalinities as Carbonate Hardness (CH) and the amount of hardness which is in excess of CH as Non-Carbonate Hardness (NCH). 

Primarily the sum of Ca and Mg salts in water, although it may include other metal salts such as Al, Mn, Sr, and Zn. Temporary hardness (carbonate hardness) is that portion of the total hardness that can combine with C03 or HC03. The balance is non-carbonate or permanent hardness and is caused by Ca or Mg nitrates/sul-fates/chlorides, etc. Permanent hardness is equivalent to the excess of hardness over alkalinity. 

Porter-Clark The original name for the cold lime-soda process. A water-softening process using sodium carbonate and calcium hydroxide. It removes the non-carbonate, as well as the bicarbonate, hardness. Developed by J. H. Porter. See Clark. 

As for carbanions, the reactivity of anionic non-carbon nucleophiles depends on the cation. The nucleophilicity and basicity of a given anionic nucleophile will usually be enhanced if it does not form strong bonds either with the cation or with the solvent. Hard cations, for example Li+ or Ti4+, will significantly reduce the reactivity of hard anions (RO-, R2N , F ), whereas soft cations (Cs+, Cu+, Pd2+) will form strong bonds with soft anions (RS , I , CN , H , R ) and thereby reduce their reactivity. 

We have seen that stray current can hardly induce corrosion on passive steel in non-carbonated and chloride-free concrete. However, the potential adverse effects of stray current on concrete structures may become increasingly important with the increased use of underground concrete construction. Stray-current effects are rarely recognised as such. The importance increases further due to the increase of the required service lives (i. e. 100 y or more). 

Similarly, lime or caustic soda are used to provide hydroxide for precipitation of magnesium hardness as Mg(OH)2. Hardness may also be present in non-carbonate form as sulphate, chloride, or nitrate. In the case of non-carbonate calcium compounds, carbonate for precipitation is provided by adding sodium carbonate (soda ash) ... 

Another approach to carbonless electrode is to use a non-carbon catalyst-support that meets the requirements of a support. Since metallic supports will corrode faster than carbon, they can hardly be used, unless they can be completely coated by a thin layer of Pt skin to avoid corrosion. Many ceramic materials can meet the stability requirement, but they lack of electronic conductivity. Again, this will not be a problem if these particles can be coated by an electronically conducting Pt thin layer. Chhina used semi-conducting indium tin oxide (ITO) particles to support Pt and achieved an average Pt crystallite size of 13 nm. Pt supported on ITO showed extremely high thermal stability and only lost 1% wt. of materials versus 57% wt. for Pt supported on Hispec 4000 carbon upon heating to 1000 °C. 

On the other hand, C02-consuming processes will hardly change the picture from non-carbon containing fuel [416]. 

---