The Base Bath

The long-term effects of glass remaining in a base bath are as follows  

An etching (frosting) of the glass could increase the ability of contami- 

The ability of high-vacuum stopcocks to maintain a vacuum may be lost. 

The ceramic decals on glassware (including volumetric marks) may be 

Volumetric glassware is likely to exhibit increased volumes. 

---

Caution. Chlorotributylstannane and l-(tributylstannyl)indene should be considered toxic and thus should be handled with gloves in an adequate fume hood. All glassware and equipment should be treated with a saturated KOH/isopropanol base bath before being taken out of the fume hood. The base bath can later be disposed with the waste tin compounds. 

However, there are disadvantages to the base bath. First, it has some safety hazards. The alcohol is a potential fire hazard, and the bath s alkalinity is caustic to skin. The base bath is also a mild glass stripper. That is, instead of cleaning the glassware, it actually removes layers of glass (and any adjoining contamination). 

Therefore, glassware should not soak in a base bath for an extended period of time, and the base bath should never be used for volumetric ware. 

Organic stopcock greases are insoluble in a base bath and will prevent the base bath from cleaning any contamination beneath the grease. 

After the base bath has been drained, let the pump soak for a few minutes with an acid rinse (to stop any alkaline reactions on the glass surface). After three or four water rinses, follow with a distilled water rinse and finally some methanol to speed the drying process. Do not blow air through the pump to speed the drying process as most compressed air is full of oils and other particulates (although dry nitrogen is acceptable). Alternatively, you can place the house vacuum hose to the pump and draw the ambient air through the pump. Remember, any acids or bases must be neutralized before disposal. 

Attention is directed to the fact that ether is highly inflammable and also extremely volatile (b.p. 35°), and great care should be taken that there is no naked flame in the vicinity of the liquid (see Section 11,14). Under no circumstances should ether be distilled over a bare flame, but always from a steam bath or an electrically-heated water bath (Fig.//, 5,1), and with a highly efficient double surface condenser. In the author s laboratory a special lead-covered bench is set aside for distillations with ether and other inflammable solvents. The author s ether still consists of an electrically-heated water bath (Fig. 11, 5, 1), fitted with the usual concentric copper rings two 10-inch double surface condensers (Davies type) are suitably supported on stands with heavy iron bases, and a bent adaptor is fitted to the second condenser furthermost from the water bath. The flask containing the ethereal solution is supported on the water bath, a short fractionating column or a simple bent still head is fitted into the neck of the flask, and the stUl head is connected to the condensers by a cork the recovered ether is collected in a vessel of appropriate size. 

Place 1 0 g. of the monobasic acid and 2 g. of aniline or p-toluidine in a dry test-tube, attach a short air condenser and heat the mixture in an oil bath at 140-160° for 2 hours do not reflux too vigorously an acid that boils below this temperature range and only allow steam to escape from the top of the condenser. For a sodium salt, use the proportions of 1 g. of salt to 1 5 g. of the base. If the acid is dibasic, employ double the quantity of amine and a reaction temperature of 180-200° incidentally, the procedure is recommended for dibasic acids since the latter frequently give anhydrides with thionyl chloride. Powder the cold reaction mixture, triturate it with 20-30 ml. of 10 per cent, hydrochloric acid, and recrystallise from dilute alcohol. 

Nate 1. Care should be taken that no solid crust of THF is formed on the bottom of the flask if it is, the bath should be removed temporarily and addition of the base interrupted. 

There are several methods for introducing the insoluble deposits into the fabric stmcture. The multiple bath method, in which the fabric is first impregnated with a water-soluble salt or salts in one bath and is then passed into a second bath which contains the precipitant, is used most often. Most semidurable retardants used on cotton are based on a combination of phosphoms and nitrogen compounds (25). 

Thickness of the laminar layer is deterrnined both by the need to reproduce fine detail in the object and by the penetration depth of the actinic laser light into the monomer bath (21,76). There is thus a trade-off between precision of detail in the model and time required for stereohthography, ie, the number of layers that have to be written, and an optimum Light-absorbing initiator concentration in the monomer bath corresponding to the chosen layer thickness. Titanocene-based initiators, eg, bis-perfluorophenyltitanocene has been recommended for this apphcation (77). Mechanistic aspects of the photochemistry of titanocenes and mechanisms of photoinitiation have been reviewed (76). 

Pt—Q—Salt, [Pt(NH3)2(HP04)] and [Pt(OH)3] (259,260). Chloride-based baths have been superseded by P-Salt-based baths, which are more stable and relatively easily prepared. Q-Salt baths offer even greater stabiUty and produce hard, bright films of low porosity. Plating under alkaline conditions employs salts of [Pt(OH3)] . These baths are easily regenerated but have low stabiUty. Platinum films have uses in the electronics industry for circuit repair, mask repair, platinum siUcide production, and interconnection fabrication (94). Vapor deposition of volatile platinum compounds such as [Pt(hfacac)2] and... 

Nonmineralized SGA flows freely, and is often known as sandy alumina because it easily covers the cryoflte bath of aluminum electrolysis cells (see Aluminum compounds, introduction). Properties typical of a sandy SGA are shown in Table 1. Aluminum smelting technology in the United States is primarily based upon sandy alumina. Older European smelting technology, however, is based upon a poor flowing, low bulk density, highly mineralized SGA called floury alumina, composed principally of a-Al O. ... 

Fig. 2. Downs cell A, the steel shell, contains the fused bath B is the fire-brick lining C, four cylindrical graphite anodes project upward from the base of the cell, each surrounded by D, a diaphragm of iron gau2e, and E, a steel cathode. The four cathode cylinders are joined to form a single unit supported on cathode arms projecting through the cell walls and connected to F, the cathode bus bar. The diaphragms are suspended from G, the collector assembly, which is supported from steel beams spanning the cell top. For descriptions of H—M, see text.

---