Calcium equivalent weight

Barium reduces the oxides, haUdes, and sulfides of most of the less reactive metals, thereby producing the corresponding metal. It has reportedly been used to prepare metallic americium via reduction of americium trifluoride (13). However, calcium metal can, in most cases, be used for similar purposes and is usually preferred over barium because of lower cost per equivalent weight and nontoxicity (see Actinides and transactinides). 

In 1817 Dobereiner found that if certain elements were combined with oxygen in binary compounds, a numerical relationship could be discerned among the equivalent weights of these compounds. Thus when oxides of calcium, strontium, and barium were considered, the equivalent weight of strontium oxide was approximately the mean of those of calcium oxide and barium oxide. The three elements in question, strontium, calcium, and barium were said to form a triad. 

Equivalent weight or gram equivalent, a mole divided by the valency of the substance. Example a mole of sodium chloride — 58.45 g, valency = 1, therefore equiv. wt = 58.45. A mole of calcium carbonate = 100.08 g, valency = 2, therefore equiv. wt. = 50.04. 

A medication orders 5.5 mEq Ca++. What is the amount of calcium dihydrate (equivalent weight of CaCl2-2H20 = 73.5) needed ... 

Only rarety is the sulfate of the nitrated base so insoluble that it separates directly on dilution of the reaction mixture as in the above example. In many cases, the hydrochloride can be precipitated by the addition of salt. Frequently, however, it is necessary to neutralize the entire amount of sulfuric acid in order to isolate the product, but this cannot be done with lime because then calcium sulfate would be precipitated with the base. In industrial preparations, tlie neutralization is done with magnesia, of which only a small amount is required because of its low equivalent weight, or with ammonia. In the latter case, the filtrate is treated with lime and the ammonia is recovered and used again. It is preferable to cany out the neutralization in steps, because most of the impurities are precipitated mst, and the later fractions are pure. 

To calculate the hardness of a particular water the concentration of actual magnesium or calcium salt is converted to an equivalent weight of calcium carbonate. Hardness is generally expressed as equivalent parts per million (p.p.m.) of calcium carbonate irrespective of the actual salt present. By defmation, 1° English hardness... 

Where surfactants were used in these experiments they were present in relatively large concentration. Hill and Lake, for example, injected a solution containing 0.046 meq/ml of a surfactant mixture having an average equivalent weight of 410 thus, the surfactant concentration was about 1.9 wt.%. Since this concentration is far above the CMC for the surfactants involved, multivalent cations may be bound by the micelles with the result that calcium sulfonate precipitation does not occur. 

The calcium tolerance of a selected group of crude alkylbenzene sulfonates is summarized in Table II. These results, while relatively imprecise, indicate that the calcium tolerance of these surfactants in dilute solutions is quite low. In general, the calcium tolerance decreases as the equivalent weight increases, and the addition of 3 wt.% n-butanol or 2-butanol does not appear to improve stability. Finally, the onset of precipitation does not appear to be very sensitive to temperature. 

Salting-out of alkylbenzene sulfonates from relatively dilute solutions by NaCl has been found to be substantial if the alkyl chain contains more than about 12 carbons. Similarly, the multivalent cation tolerance of alkylbenzene sulfonates in dilute solutions has been found to be small and strongly dependent on equivalent weight. In general, if the equivalent weight exceeds 350 (alkyl chain more than 12 carbons), the calcium tolerance appears to be extremely small. The addition of short-chain alcohols appears to be of limited benefit in preventing either salt-ing-out by NaCl or multivalent cation precipitation. 

Ten mmol(- -) kg-1 OH consumed during the titration is equivalent to 4.5 tonnes pure CaCC>3 (ha-30 cm)-1 of field soil. The mol(+) equivalent weight of CaCC>3 is 100 in tins case because only one OH " is produced per CaC03 molecule, in the normal pH range of limed acid soils. Although many people still regard the primary effect of lime to be the provision of adequate soil calcium, its main value is really to... 

Calcium carbonate does not always have an equivalent weight of 50 g/mole, however. In the following reaction,... 

In a series of experiments and measurements performed in the writer s laboratory, it was shown that the range of heat outputs can be vastly extended by using strontium and (even better) calcium chromate in lieu of the barium chromate (Table 23). Because of the lower equivalent weight of the alkaline earth ballast in the calcium chromate, the peak calories per gram for series of mixtures with boron... 

An equivalent weight of precipitated BaCOs (93g) may be used instead for BaS04 but the volume of concentrated HCl in preparing the PdCl2 solution should be reduced to 8.2ml (to avoid decomposition of the carbonate) to give 5% Pd on calcium carbonate catalyst. [Mozingo Org Synth Coll Vol HI 685 7955.]... 

Titrate Harleco EDTA, Item No. 3854, was diluted with H2O to a concentration such that 1 ml was approximately equal to 0.02 mg of CaC03. (Calcium equivalent of 8 /xg/ml). To 800 ml of this solution was added 40 ml of l o, by weight, NaCN (aqueous), 40 ml of 5N NaOH, and 10 ml of Calcein solution (made by dissolving 0.25 g of Calcein in 4 ml of IN NaOH and 30 ml H2O and diluting 1 100 with H2O). One milliliter of this solution contained a calcium equivalent of 7.2 fig. Twenty milliliters was used for each titration. 

Isocyanate prepolymers with NCO equivalent weights of 10()0-2000 are used in the formulation of one-component urethane sealants. A typical gun-grade compounds may contain 30-60% of prepolymer, pigmented with titanium dioxide, calcium carbonate, and silica, with up to 5% of dry toluol for easier gunning. Compounds may also contain molecular sieves to absorb unremoved water for improved compound stability. As with one-component polysulfide sealants, manufacture of the compound is carried out with dry ingredients under vacuum and heat so as to eliminate all traces of water. One suggested formulation is shown in Table 20. 

The equivalent weight of calcium carbonate is one-half its formula weight because only one-half of a CaC03 molecule is required to neutralize one OH". Expressing alkalinity in terms of mg/L of CaC03 can, however, lead to confusion, and equivalents/L is preferable notation for the chemist. 

In dealing with electrolytes, it is frequently advantageous to take into account the valence of the ions and to express amounts in equivalents or milliequivalerUs. The equivalent weight is the atomic or molecular weight divided by the valence of the ion. In the case of calcium, for example, 1 milliequivalent equals 40.1 mg divided by 2, (the atomic weight of calcium is 40.1), which is electrochemically equivalent to 1 milliequivalent of Na or 23 mg. Concentrations are measured by the unit milliequivalent per liter, which is abbreviated as meq/liter. We shall make much use of this unit. 

Calcium Chloride Solution Q%fL)—Transfer l.(XX)g of calcium chloride (CaQ2), or the equivalent weight of a hydrated salt, into a 100-mL volumetric flask and dissolve in 25 mL of water. Dilute to the mark with mixed alcohol solvent. 

Gum ghatti is the calcium and magnesium salt of a complex polysaccharide which contains L-arabinose, D-galactose, D-mannose, and D-xylose and D-glucuronic acid (48) and has a molecular weight of approximately 12,000. On dispersion in water, gum ghatti forms viscous solutions of viscosity intermediate between those of gum arabic and gum karaya. These dispersions have emulsification and adhesive properties equivalent to or superior to those described for gum arabic. 

---