Calcium hydroxide wash paper

Table IV shows brightness retention of newsprint papers. Borohy-dride treatment increased initial brightness by as much as 10 brightness units. A decrease in brightness is generally observed when newsprint is subjected to a Ca(OH)2 wash. Treatment with either 0.1 or 1.0 NaBH4 followed by 0.002 calcium hydroxide washing also increased the brightness of newsprint. For the newsprint samples, the borohydride treatment did not produce a significantly greater improvement in brightness retention than the calcium hydroxide wash alone.

Table V. Effect of Calcium Hydroxide Wash Concentration on Aging of Foldur Kraft Paper ...

The treatment of bleached kraft pulp with sodium borohydride followed by incorporation of basic calcium salts increased the stability of paper made from this pulp by 1.5-2.6 times. When manufactured paper, rather than pulp, was subjected to sodium borohydride treatment followed by washing with an aqueous solution of calcium hydroxide, the stability of the paper increased by as much as 4 times for groundwood paper and 30 times for bleached kraft paper. 

Treatment of Papers. Foldur kraft and newsprint papers were prewet with 1 1 solution of denatured alcohol and distilled water before further treatment to facilitate their penetration. Test papers were treated with sodium borohydride by immersion in the appropriate solution for 30 min. The treated samples and untreated controls were then washed for 1 h in either a wash solution composed of dilute calcium hydroxide or in deionized water, or they were left unwashed. 

The effect of a reducing sodium borohydride treatment followed by a mildly alkaline wash on the physical properties and stability of paper was studied. Test papers were characterized by measuring their initial pH value, brightness, and folding endurance. Then they were subjected to borohydride treatment and washed with dilute calcium hydroxide solution or deionized water. The concentrations of sodium borohydride... 

Six groups of paper were subjected to the following treatments Paper A - this paper was washed as described Paper B -the washed papers were soaked In Mg(HC03)2 for one-half hour and dried Paper C - the washed papers were soaked in 0.02 g/1 copper acetate solution for 30 minutes and alr-drled. They were then soaked for 30 minutes In the magnesium bicarbonate solution and alr-drled. This paper showed 86 ppm copper by atomic adsorption analysis Paper D - washed papers were soaked in 0.0159 g/1 copper acetate solution for 30 minutes and alr-drled. They were soaked in calcium hydroxide solution for 15 minutes, then calcium bicarbonate solution for 15 minutes and air-dried. This paper showed 64 ppm copper by analysis Paper E - washed papers were soaked in 0.0089 g/1 copper acetate solution, for 60 minutes and air-dried. Analysis indicated 59 ppm copper Paper F - washed papers were soaked in calcium hydroxide solution for 15 minutes, then in calcium bicarbonate solution for 15 minutes and alr-drled. 

The filtrate (at 25 to 40 ) is stin ed continuously while 80 g. of calcium hydroxide (slaked lime) is added over a period of about K hour. Stirring is continued for H hour longer. The slurry is then heated to 65 to 75 and stirred vigorously while additional hydroxide is added until the slurry is strongly alkaline toward litmus paper, and stirring is continued for 3 hour longer. An excess of lime does no harm other than to add to the bulk of the solids to be filtered out and washed. 

The hot slurry is filtered by suction. The filter cake is washed with 300 ml. of water saturated with calcium hydroxide at 65 . The filter cake is slurried in 400 ml. of water saturated with calcium hydroxide at 65 and refiltered. The residue is washed with 200 ml. of hot water saturated with calcium hydroxide. The filtrates and washings are combined. If the solution now does not show strong alkalinity to litmus paper, a little more lime should be added and the solution refiltered. 

Method 2. Transfer the dark-coloured reaction product to a separatory funnel and shake successively with water, with sufficient 5-10 per cent, sodium hydroxide solution to ensure that the washings are alkaline to litmus, and finally with water. Dry with anhydrous magnesium sulphate or calcium chloride. Filter through a fluted filter paper into a small distilling flask and distil slowly. Collect the crude bromobenzene at 150-170° pour the residue whilst still hot into a small porcelain basin. Redistil the hquid of b.p. 150-170° (3) and collect the bromobenzene at 154-157° the yield is about 60 g. 

The acid, without drying, is suspended in about 200 cc. of distilled water and with vigorous stirring, cautiously (Note 3) treated with 25 per cent sodium hydroxide solution until dissolved and the solution reacts neutral to litmus. The solution is then filtered through folded filter paper which should be free from soluble calcium salts, otherwise the filtrate will remain clouded by a suspension of the calcium salt. The clear, faintly yellow or colorless filtrate is then vigorously stirred and treated with 1.5 volumes of 95 per cent alcohol. Crystallization is induced by rubbing with a rod and then an additional volume of alcohol is added. The mixture should be allowed to cool to about 200 and stand for at least two hours to complete the precipitation of the salt, which is then filtered by suction and washed thoroughly with 85 per cent alcohol. The salt is then air-dried. The yield is 73-77 g. (38-40 per cent of the theoretical amount). 

A less specific type of adsorption can sometimes be used if the required product forms insoluble hydroxides but the target element does not. In this case, the solution is made alkaline, and the carrier-free radio-colloidal product is readily absorbed on to filter paper in good yield, when, after washing, it can subsequently be dissolved in acid. This has been used for the separation of magnesium from aluminium, scandium from calcium and for several other elements (17), (26), (42), (44), (66), (103), (104), (105), (106). 

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