Carbonate stop baths

Developers should be kept in brown amber glass bottles, particularly if stored for more than a few weeks. This is because developers easily oxidize and lose their potency when exposed to air and/or light. Plastic bottles breathe and will speed the rate of oxidation. High-density polyethylene storage bottles are suitable for solutions of fixer, stop bath, bromide, carbonate, and just about anything except developers. 

Balanced Alkali is a proprietary chemical of Eastman Kodak, and until recently it was known as Kodalk . Balanced Alkali is more alkaline than borax and more easily soluble, but less alkaline than carbonate. As Balanced Alkali contains no free carbonate, there is no danger of carbonic gas bubbles being formed when an acid stop bath is used (see the next section, Moderate Alkalis). Balanced Alkali can be substituted for carbonate (Conversion Tables Alkali Substitutions), and for almost all purposes it is identical to sodium metaborate. 

Carbonate has one important drawback. When a large amount is used carbonic gas bubbles can form in the emulsion of either film or paper when transferred to an acetic stop bath, resulting in pinholes and/or reticulation. Using a less acid stop bath, such as Kodak SB-1 Nonhardening Stop Bath or a running water bath, should prevent this from occurring. 

Notes Sodium carbonate releases a gas when added to an acid stop bath or an acid fixing bath this gas may cause pinholes, or blistering, to develop in film emulsions. 

Mix 30 g. (38 ml.) of iaopropyl alcohol with 450 g. (265 ml.) of constant boiling point hydriodic acid (57 per cent.) (Section 11,49,2) in a 500 ml. distilling flask, attach a condenser for downward distillation, and distil slowly (1-2 drops per second) from an air bath (compare Fig. II, 5, 3). When about half the liquid has passed over, stop the distillation. Separate the lower layer of crude iodide (80 g.). Redistil the aqueous layer and thus recover a further 5 g. of iodide from the flrst quarter of the distillate (1). Wash the combined iodides with an equal volume of concentrated hydrochloric acid, then, successively, with water, 5 per cent, sodium carbonate solution, and water. Dry with anhydrous calcium chloride and distil. The isopropyl iodide distils constantly at 89°. 

In a 250 ml. conical flask, fitted with an air condenser of wide bore, place 50 g. (51 -5 ml.) of acetonylacetone (see Section V,9, Note 2) and 100 g. of ammonium carbonate (lump form). Heat the mixture in an oil bath at 100° until effervescence stops (60-90 minutes) some ammonium carbonate (or carbamate) sublimes into the condenser and this must be pushed back into the reaction mixture by means of a stout glass rod. Replace the air condenser by a Liebig s condenser with wide bore inner tube and reflux the mixture gently (bath temperature, 115°) for a further 30 minutes dissolve the solid which has sublimed into the condenser in about 5 ml. of hot water and return the solution to the reaction mixture. 

In a 500-cc. round-bottom flask (Note i) fitted with a mechanical stirrer and surrounded by an ice-salt cooling bath, are placed 54 g. (0.71 mole) of carbon disulfide and 90 cc. (1.3 moles) of concentrated ammonium hydroxide (sp. g. 0.9). The stirrer is started and 56 g. (0.6 mole) of aniline (Note 2) is run into the mixture from a separatory funnel at such a rate that the addition is complete in about twenty minutes. The stirring is continued for thirty minutes after all of the aniline has been added, and then the reaction mixture is allowed to stand for another, thirty minutes. During this time a heavy precipitate of ammonium phenyl dithiocarbamate separates and may even stop the stirrer. 

In a 5-I. round-bottomed flask, 500 g. (5.3 moles) of chloro-acetic acid (Note 1) is dissolved in 700 cc. of water. The solution is warmed to 50°, neutralized with 290 g. (2.7 moles) of anhydrous sodium carbonate, and again cooled to room temperature. Meanwhile, 294 g. (6.0 moles) of sodium cyanide (97 per cent) is dissolved in 750 cc. of water warmed to 55°, the solution is cooled to room temperature, and then added to the sodium chloroacetate solution, with rapid mixing of the two solutions and cooling under the water tap. When the solutions are completely mixed, the cooling is stopped and the temperature allowed to rise. When it reaches 95° the solution is cooled by adding 200 cc. of ice water, and this is repeated, if necessary, until the temperature no longer rises (Note 2). The solution is then heated on the steam bath for one hour to ensure completion of the reaction. 

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