Glassware colour

K2CO3 (from KOH and CO2), used chiefly in high-quality decorative glassware, in optical lenses, colour TV lubes and fluorescent lamps il is also used in china ware, textile dyes and pigments. 

If die number of experimental factors is less that of a standard design (a multiple of 4 minus 1), die final factors are dummy ones. Hence if there are only 10 real factors, use an 11 factor design, the final factor being a dummy one this may be a variable diat has no effect on the experiment, such as the technician diat handed out die glassware or die colour of laboratory furniture. 

The appropriate negative control is a sample of methanol treated in exactly the same way as the sample mixture, but without the addition of the fungal material. This shows that the glassware, solvent, glass wool and pipette are free from contamination with compounds which could react in the colour test. 

Use cleaned plastic collection tubes with stoppers. The whole set (tube and stopper) must be tested to deliver less than 10% extraneous amounts of cadmium. Do not use coloured stoppers. Do not use plastics with a Cd-softener. Before starting the study test 6 test tubes per tube production lot. During the study frequently test blank tubes, e.g. for 1% of the total number of samples to study. Test may be performed with a 1% v/v solution of nitric acid (e.g. Suprapur quality) in bidistilled water. Preferably use vacuum collection tubes. No special type of needles is required. Needles of stainless steel are adequate. Other needles, e.g. siliconized or iridium needles may be used as well but are not necessary. Use vinyl gloves, free of talc. Use cleaned plastic test tubes. See further collection tubes. Do not use glassware. 

Procedure. Once the glassware is dry, equip around-bottomed flask with a magnetic stirrer bar and a rubber septum and flush this with argon. A balloon of argon can be used to maintain the inert atmosphere during the reaction. Add diphenyldiselenide (5.9 g, 19 mmol) and anhydrous ethanol (100 ml, distilled from CaH2) and cool the reaction to 0 °C using an ice bath. The solution will be a yellow colour, due to the diphenyldiselenide. Dissolve the sodium borohydride (1.43 g, 38 mmol) in... 

Aventurine. A decorative effect achieved on the surface of pottery or glass by the formation of small, bright, coloured crystals (generally hematite, Fc203, on pottery bodies, but chrome or copper on glassware). 

Engraving. A method of decoration. For application to pottery, the pattern is engraved on a copper plate or roller the incised pattern is then filled with specially prepared colour which is transferred to the ware by transfer paper. As a method of decorating glassware, the pattern is cut directly into the glass surface by means of copper wheels ... 

Striking. (1) The development of opacity or colour in glassware by a heat-treatment process, e.g. by the formation of a colloidal dispersion, within the glass, of a small amount of Cu, Ag or Au. 

A variant, said to be more objective, is the method of Tsubouchi et aL [6], in which the colour remains in the organic layer throughout. The colour change is very sharp. The authors do not say why they used such dilute solutions or such small volumes. With dilute solutions of surfactants, especially quats, losses of solute through adsorption on to the glassware can cause serious errors. With small volumes, small absolute errors are large in relative terms. However, the procedure as reported is as follows. 

Clean all glass- and plastic-ware with a brush and a detergent solution followed by a thorough rinse with water. The detergent must be stringently tested for phosphate. Glassware used for the colour development should be reserved exclusively for phosphate determination. 

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