Water glass solutions

Many methods exist for the production of phosphor screens [5.296]. For monochromatic tubes a suspension of the phosphor in alcohol or water, with addition of water glass solution, is placed in the tube and is deposited by sedimentation on the inner surface of the faceplate. The adhesion is effected by the slowly precipitating silicic acid. 

To study these reactions use a M solution of sodium silicate, Na2Si03. Commercial (30%) water-glass solutions should be diluted with a five-fold amount of water. 

Sodium silicate (m). Dilute 200 ml commercial (30%) water glass solution with water to 1 litre. 

Alkali silicate powders are produced by spray or drum drying of water glass solutions, which still contain ca. 20% water. They dissolve upon heating with a little water forming water glass solutions. 

Potassium water glass solutions are mainly utilized in the production of coatings for welding electrodes, as binders for luminescent pigments used in cathode ray tubes, for impregnating walls and as a binder for plasters. 

In precipitation processes acid is added to a water-glass solution and acid, generally H2SO4, simultaneously with water in a large agitator vessel. 

If the water-glass solution is reacted with alkaline earth or aluminum salts, silicates are obtained instead of silicas. 

Method B (Vacuum-sol method) A 0.96M aluminum nitrate solution was added to 50ml water glass solution until the Si/Al molar ratio was attained. The precipitate was collected by centrifugation and washed 7 times to remove the sodium ions. After washing, the precipitate was put into 200ml of water and then added a certain quantity of 0.94M nitric acid to peptize the precipitate to obtain the sol sample. The prepared sol was dried at room temperature in a vacuum box until it began to form the gel sample. The gels were also calcined at 550 C in air for 10 hours. The sol and solid samples produced by method B were defined as VSG samples [5]. 

Variations of Silica Sol Manufacturing Process. As shown in Figure 4, the four methods, A-l, A-2, B-l, and B-2, use different technical combinations of nucleation, particle growth, and concentration. In any of these methods the raw material aqueous water-glass solution is diluted, and sodium is removed with a cation-exchange resin to obtain an active silicic acid. The characteristics of these four processes are shown in Table I. 

The hydrothermal synthesis of NaY in the presence of MB is carried out according to the recipe given above. MB is added in three different ways lO" moles MB are added to the sodium water glass solution (sample 1) or to the aluminate solution (sampie 2) or to the siurry containing the NaX seeds (sample 3). The coloured NaY crystals are subjected to the extraction procedure, characterizations and opticai spectroscopy like the ion-exchanged samples. 

The analysis of the crystallinity of the MB-template loaded zeolite crystals by nitrogen physisorption at 77 K gives no reductions of the Nz uptake capacity valid for NaY (ca. 170 ml Nz (NTP)/g dry faujasite) if the MB was added to the aluminate or water glass solutions (samples 1 and 2) prior to the gel formation. A drastic (ca. 40%) reduction of the Nz uptake capacity is found if the MB is added with the NaX seeds (sample 3) after the gel formation. The water uptake capacity of samples 1-3 is comparabie to the vaiue for dye-free NaY, i.e. ca. 25 wt%. 

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