Base bath

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 Chloride-based baths have been superseded by P-Salt-based baths, which are more stable and relatively easily prepared.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... 

There appear to be no cases of selenide deposition from acidic baths. Se-lenosulphate is not stable under even mildly acidic conditions, and all selenourea-based baths have been alkaline ones. 

This section deals only with thiourea-based baths. There is little variation in the thiosulphate baths that have been reported. 

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. 

The electrodeposition of chromium in a mixture of choline chloride and chromium(III) chloride hexahydrate has been reported recently [39]. A dark green, viscous liquid is obtained by mixing choline chloride with chromium(III) chloride hexahydrate and the physical properties of this deep eutectic solvent are characteristic of an ionic liquid. The eutectic composition is found to be 1 2 choline chloride/chromium chloride. From this ionic liquid chromium can be electrode-posited efficiently to yield a crack-free deposit [39]. Addition of LiCl to the choline chloride-CrCl3-6H20 liquid was found to allow the deposition of nanocrystalline black chromium films [40], The use of this ionic liquid might offer an environmentally friendly process for electrodeposition of chromium instead of the current chromic acid-based baths. However, some efforts are still necessary to get shining... 

Prolonged cleaning by base baths or HF can remove ceramic markings. 

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. 

Important note. A base bath can be stored in a plastic (OK) or stainless steel (best) container. This solution is highly basic, and as such it will dissolve a glass container. The alcohol in a base bath is flammable, and it therefore presents a problem for plastic containers that would be likely to melt or bum. 

Base baths can be used over and over until they begin to show a decrease in effectiveness. Between use, a base bath should be covered to prevent evaporation and to prevent other glassware from inadvertently falling in. 

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

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

Disposal. As a base bath is used, it tends to lose volume both to evaporation and to the small loss incurred each time an object is removed carrying some base bath with it. The remaining base bath can be recharged by adding to it a new solution, so disposal is seldom necessary. If you wish to dispose of the remaining solution, as long as the base has been neutralized (check with litmus paper) and contains no heavy metals, it can be rinsed down the sink. However, check with local environmental and safety laws to see if any other concerns need to be addressed. 

There are few occasions where HF is recommended over a safer glass stripper or a base bath (see Sec. 4.1.7). The biggest demand for HF as a cleaner is to remove bumt-on particulate matter from a glass surface. For example, if silicone... 

Use a small amount of heated sulfuric acid in a fume hood. Roll the item around so the acid comes in contact will all areas of the piece. Unless the item needs to soak (for example, 30 minutes of soaking time is recommended for the removal of silicone grease), immediately empty the glassware and rinse. Although more dangerous to use than a base bath, this technique can be used to remove silicone grease from volumetric ware without concerns about altering the volume of volumetric ware. 

If your pump used silicone oil and has left crusty remains that will not drain, a base bath is recommended (see Sec. 4.1.7). Place a cork in the end of the drainage tube (fire-polish as before), pour in a base bath solution, and let the pump sit for an hour or two. Because a base bath is highly flammable, be sure to unplug all electrical components of the pump before you begin this type of cleaning process. 

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. 

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