Reagent Solution Neutralization

Although sodium hydroxide may be delivered as a 50% solution, it begins to crystallize at 12°C, so immediate dilution into storage is recommended.16 

---

Crushed limestone preneutralization Reagent solution neutralization ... 

Steroids The applied steroids are reduced by means of a mixture of 10% ethanolic sodium borohydnde solution and 0 1 N sodium hydroxide solution (1-1-1) The excess reagent is neutralized with aad after 30 min [3]... 

Anthranilic acid. Cadmium ( > 100 mg in 150 mL). Add 3 per cent sodium anthranilate solution to the boiling solution (neutral or weakly acid). Filter and wash the precipitate with 50mL of diluted reagent (1 20), then with ethanol. Dry at 105-110 °C and weigh as Cd(C7H602N)2 (Section 11.21). 

Water neutralized with limestone and reagent solution was stripped of carbon dioxide by spraying, followed by settlement in a basin, then filtration through a dam of straw bales, except that effluent from the limestone-packed flume was not subsequently treated. A small copper cementacion unit was also operated. 

An alkali-detergent solution is used during the recovery of plasmid DNA. The alkaline pH causes the chromosomal DNA to be irreversibly denatured while the plasmid is reversibly denatured. The mixture is subsequently neutralized by the addition of a suitable reagent. At neutral pH, the plasmid DNA renatures and remains in solution while the denatured chromosomal DNA precipitates, forming a complex network with other materials, such as proteins and cell debris. The precipitated material flocculates and transforms into a porous gel over a period of 1 to 2 hours. The gel slowly floats to the surface, leaving behind in the solution the plasmid DNA and the fine particulates. 

A commercial fertilizer is a material that contains at least one of the plant nutrients in chemical form that, when applied to the soil, is soluble in the soil solution phase and assimilable or available by plant roots. Most often, this implies chemical forms that are water soluble. However, in the case of phosphorus, solubility in special reagent solutions (citric acid, neutral ammonium citrate, or alkaline ammonium citrate) often is used as a guide for availability to plants. In the case of nitrogen, slow solubility in water may be more desirable from an environmental and efficiency standpoint than easy solubility. 

The pH of the solution therefore decreases. Hence if the solution is initially almost neutral to, say, bromothymol blue (green), then upon the addition of mannitol the colour becomes yellow. It is advisable when testing for minute quantities of borates to recrystallize the mannitol from a solution neutralized to bromothymol blue, wash with pure acetone and dry at 100°. The reagent (a 10 per cent aqueous solution of mannitol) may also be neutralized with 0 01m potassium hydroxide solution, using bromothymol blue (a 0 04 per cent solution in 96 per cent ethanol) as indicator. Only periodate interferes with the test it can be decomposed by heating on charcoal. 

Render the test solution almost neutral to bromothymol blue by treating it with dilute acid or alkali (as necessary) until the indicator turns green. Place a few drops of the test solution in a micro test-tube, and add a few drops of the reagent solution. A yellow colouration is obtained in the presence of a borate. It is advisable to carry out a blank test with distilled water simultaneously. 

Mix 1 drop of the test solution (neutral or faintly acid with acetic acid) with 1 drop of the benzidine acetate reagent. A blue colouration is produced. 

In this system, amphetamine, 3,4-methylenedioxyamphetamine (MDA) and the A-methyl and A-ethyl analogues of the drugs were derivatized, with 4-chloroamphetamine being used as the internal standard. For powders, solutions were prepared at concentrations of 1 mgml in methanol and a 100 til aliquot blown dry under nitrogen. To the residue was added 50 p.1 of 0.5 M KOH and 500 p,l of toluene. The mixture was then shaken for 30 s and centrifuged, after which the toluene layer was recovered and HFBA (5 til) added. The excess reagent was neutralized with 500 p,l of 10% NaHCOs and an aliquot (1 ttl) analysed by GC-MS. Each of the amphetamines and the A-alkylated derivatives could be separated and identified on the basis of retention index and mass spectral data. 

Cleaning Up Place all solutions used in this experiment in a beaker (unused ammonium hydroxide, sodium hydroxide solution used to clean out the tubes, Tollens reagent from all tubes). Remove any silver mirrors from reaction tubes with a few drops of nitric acid, which is added to the beaker. Make the mixture acidic with nitric acid to destroy unreacted Tollens reagent, then neutralize the solution with sodium carbonate and add some sodium chloride solution to precipitate silver chloride (about 40 mg). The whole mixture can be flushed down the drain or the silver chloride collected by suction filtration and the filtrate flushed down the drain. The silver chloride would go in the nonhazardous solid waste container. 

Reduction. Since the reagent is neutral, it is useful for the reduction of alkali-sensitive compounds. Thus diethyl oxaloacetate is reduced to diethyl malate by aluminum amalgam in ether solution in 70-80% yield, whereas with sodium amalgam the yield is only 50%. Nitrobenzene can be reduced to aniline in hot ethanol or,... 

The colour reaction of Chlorophosphonazo III (formula 4.11) with calcium ions gives a sensitive spectrophotometric method for calcium [28-30]. The determination may be carried out either in weakly acid solution (pH 2-3) ( e = 2.8-10 ) or in a neutral medium (pH 7). In this case the molar absorptivity is 5.4-10 at 668 nm (a =1.3) [30]. The absorbance maximum of the reagent in neutral medium is at 570 nm. 

---