Rinsing

Insufficient rinsing can also result in some codeposition if the previous reactant is not fully removed. The main drawback is the possibility of 3-D growth, which can be hard to identify with very thin deposits. Alternatively, the rinse solution may not be important. Some high quality CdTe films were formed in this group without using a separate rinse solution. That is, the reactant solutions were exchanged by each other, under potential control, suggesting some small amount of codeposition probably did occur. 

The amount of electrolyte needed in a rinse solution depends on current flow during the rinse. Rinsing can be performed at open circuit in some cases, so that no electrolyte is needed. If the amount of current during rinsing is low, electrolyte concentrations can be low as well. So far, the same electrolyte concentrations have been used for rinsing and deposition. 

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The solutions we offer are based on two main technologies electrolytic silver recovery from fixer solutions and cascade fixing. In what follows we will give more teclmical details about these teclmologies. We will clarify the key-factors to obtain reliable and more ecological solutions for the silver in the rinsing water. 

In case of cascade fixation, an additional fixing step is used to lower the silver concentration in the fixer which is carried over to the rinse section, as is shown in Figure 4. 

The process is designed such that virtually all silver is fixed in the first fixing step. The fixer in the first fixer section has a typical silver concentration of 7 g/1. The silver in the second fixer section originates from the carry-over from the first fixing section, and a typical silver concentration is 0,4 g/1. Hence, the silver carried over to the rinsing section will be substantially lower. 

Depending on the boundary conditions, the optimal technology to decrease the silver in the rinsing water, may either be electrolytic desilvering or cascade fixation. 

To comply with existing and future legislation with respect to silver content in processor rinsing water, the approach developed by Agfa is threefold. 

First, we want to offer G335SF in combination with STRUCTURIX SILVERFIX as a viable solution to customers who want to upgrade their existing equipment (installed base processors) in order to decrease the silver content of their rinsing water. 

Thirdly, a NDT-S type cascade processor will be offered. By implementing a fixing cascade in the processor, large decreases of silver content in the rinsing water are possible, even for large customers. 

In contrast to tire preparation of LB films, tliat of SAMs is fairly simple and no special equipment is required. The inorganic substrate is simply immersed into a dilute solution of tire surface active material in an organic solvent (typically in tire mM range) and removed after an extended period ( 24 h). Subsequently, tire sample is rinsed extensively witli tire solvent to remove any excess material (wet chemical preparation). 

When the solution has been boiling for hours, remove A, cool the contents, and then pour the ethanolic solution of the ester into a separating-funnel containing about 200 ml. of water, finally rinsing out the flask with a few ml. of water which are also doured into the funnel. Since the pensity of ethyl benzoate is only... 

Chill the concentrated solution of the amine hydrochloride in ice-water, and then cautiously with stirring add an excess of 20% aqueous sodium hydroxide solution to liberate the amine. Pour the mixture into a separating-funnel, and rinse out the flask or basin with ether into the funnel. Extract the mixture twice with ether (2 X25 ml.). Dry the united ether extracts over flake or powdered sodium hydroxide, preferably overnight. Distil the dry filtered extract from an apparatus similar to that used for the oxime when the ether has been removed, distil the amine slowly under water-pump pressure, using a capillary tube having a soda-lime guard - tube to ensure that only dry air free from carbon dioxide passes through the liquid. Collect the amine, b.p. 59-61°/12 mm. at atmospheric pressure it has b.p. 163-164°. Yield, 18 g. 

Cool the mixture and pour the liquid reaction product into a separating-funnel. Rinse out the flask (which may contain some unchanged zinc) with ether, pour the latter into the funnel, and extract the aqueous solution with the ether. Repeat the extrac tion with a second quantity of ether, unite the ether extracts, wash them by extracting once with water, and then dry the ethereal extract over sodium sulphate. 

The steam-distillation is continued for 5 minutes after steam can first be seen entering the condenser the ideal rate of distillation is about 4 -5 ml. of distillate per minute, but this is not critical and may be varied within reasonable limits. The receiver J is then lowered from the lip K of the condenser and the steam-distillation continued for a further two minutes, thus ensuring that no traces of liquid containing ammonia are left on the inside of the condenser. At the end of this time any liquid on the lip K is rinsed with distilled water into J, which is then ready for titration. It is important that the receiver and its contents are kept cold during the distillation and it is advisable to interpose a piece of asbestos board or other screen so that it is not exposed to the heat from the burner under the steam generator. 

Warm about loo ml. of distilled water in a beaker to about 40 and with a portion of this thoroughly rinse out the mouth and reject the liquid. Again introduce about 20 ml. of the warm water into the mouth and mix with the saliva as completely as possible. Transfer the liquid so obtained into another beaker and then filter through a small fluted filter-paper into a small conical flask or boiling-tube. 

Satisfactory cleaning may often be achieved by rinsing the vessel with a few ml. 

The apparatus depicted in Fig. 11,34, 1, intended for advanced students, may be used for the filtration of a small quantity of crystals suspended in a solvent either a Hirsch funnel or a glass funnel with Witt filter plate is employed. The mixture of crystals and mother liquor is filtered as usual through the funnel with suction. Rotation of the three-way tap wifi allow air to enter the filter cylinder, thus permitting the mother liquor to be drawn oflF by opening the lower tap. The mother liquor can then be applied for rinsing out the residual crystals in the vessel, and the mixture is again filtered into the cylinder. When all the crystals have been transferred to the funnel and thoroughly drained, the mother liquor may be transferred to another vessel the crystals may then be washed as already described (Section 11,32). 

It is preferable to use Tollen s ammoniacal silver nitrate reagent, which is prepared as follows Dissolve 3 g. of silver nitrate in 30 ml. of water (solution A) and 3 g. of sodium hydroxide in 30 ml. of water (solution B). When the reagent is requir, mix equal volumes (say, 1 ml.) of solutions A and JB in a clean test-tube, and add dilute ammonia solution drop by drop until the silver oxide is just dissolved. Great care must be taken in the preparation and use of this reagent, which must not be heated. Only a small volume should be prepared just before use, any residue washed down the sink with a large quantity of water, and the test-tubes rinsed with dilute nitric acid. 

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