In-process meaning

The ability of living organisms to differentiate between the chemically similar sodium and potassium ions must depend upon some difference between these two ions in aqueous solution. Essentially, this difference is one of size of the hydrated ions, which in turn means a difference in the force of electrostatic (coulombic) attraction between the hydrated cation and a negatively-charged site in the cell membrane thus a site may be able to accept the smaller ion Na (aq) and reject the larger K (aq). This same mechanism of selectivity operates in other ion-selection processes, notably in ion-exchange resins. 

The result of the above process means that sample molecules dissolved in a solvent have been extracted from the solvent and turned into ions. Therefore, the system is both an inlet and an ion source, and a separate ion source is not necessary. 

Many electroless coppers also have extended process Hves. Bailout, the process solution that is removed and periodically replaced by Hquid replenishment solution, must still be treated. Better waste treatment processes mean that removal of the copper from electroless copper complexes is easier. Methods have been developed to eliminate formaldehyde in wastewater, using hydrogen peroxide (qv) or other chemicals, or by electrochemical methods. Ion exchange (qv) and electro dialysis methods are available for bath life extension and waste minimi2ation of electroless nickel plating baths (see... 

Simple-cycle efficiency does not usually mean as much to process users as total-cycle efficiency, because the gas turbine is not usually economic in process applications without some type of heat recovery. Total-cycle efficiency is most important in any economic evaluation. In a cycle with heat recovery, the only major loss that is charged to the cycle is the heat exhausting from the boiler stack. With the good comes the bad. Gas turbine maintenance is generally somewhat higher in cost and should be included in the total evaluation. 

When a gas comes in contact with a solid surface, under suitable conditions of temperature and pressure, the concentration of the gas (the adsorbate) is always found to be greater near the surface (the adsorbent) than in the bulk of the gas phase. This process is known as adsorption. In all solids, the surface atoms are influenced by unbalanced attractive forces normal to the surface plane adsorption of gas molecules at the interface partially restores the balance of forces. Adsorption is spontaneous and is accompanied by a decrease in the free energy of the system. In the gas phase the adsorbate has three degrees of freedom in the adsorbed phase it has only two. This decrease in entropy means that the adsorption process is always exothermic. Adsorption may be either physical or chemical in nature. In the former, the process is dominated by molecular interaction forces, e.g., van der Waals and dispersion forces. The formation of the physically adsorbed layer is analogous to the condensation of a vapor into a liquid in fret, the heat of adsorption for this process is similar to that of liquefoction. 

From this relatively simple test, therefore, it is possible to obtain complete flow data on the material as shown in Fig. 5.3. Note that shear rates similar to those experienced in processing equipment can be achieved. Variations in melt temperature and hypostatic pressure also have an effect on the shear and tensile viscosities of the melt. An increase in temperature causes a decrease in viscosity and an increase in hydrostatic pressure causes an increase in viscosity. Topically, for low density polyethlyene an increase in temperature of 40°C causes a vertical shift of the viscosity curve by a factor of about 3. Since the plastic will be subjected to a temperature rise when it is forced through the die, it is usually worthwhile to check (by means of Equation 5.64) whether or not this is signiflcant. Fig. 5.2 shows the effect of temperature on the viscosity of polypropylene. 

The wide array of choices available to research chemists necessitates a diligent search for hazards to select the inherently safest chemistry. One of the means to search for hazards is to conduct a literature search, looking in particular for reports of incidents occurring in processes using the same or similar process chemistry being considered. 

To limit the potential for deficiencies to escape detection before the product is released, special processes should be documented in the form of procedures and specifications that will ensure the suitability of all equipment, personnel, and facilities, and prevent varying conditions, activities, or operations. Qualification in the context of special processes means that you need to conduct a thorough assessment of the processes to determine their capability to maintain or detect the conditions needed to produce conforming product consistently. The limits of capability need to be determined and the processes only applied within these limits. In qualifying the processes you need to qualify the personnel using them by training and examination as well as the materials, equipment, and facilities employed. It is the combination of personnel, materials, equipment, and facilities which ensure qualified processes. 

In continuous production, product is inspected by taking samples from the line which are then examined while the line continues producing product. In such cases you will need a means of holding product produced between sampling points until the results of the tests and inspections are available. You will also need a means of releasing product when the results indicate that the product is acceptable. So a Product Release Procedure or Held Product Procedure may be necessary. The standard implies, however, that if you have released product under positive recall procedures you do not need to hold product while in-process inspection and tests are performed. The reference to clause 4.10.3(a) is also ambiguous because the inspections and tests carried out in accordance with the quality plan or documented procedures may not cover those necessary to verify product on receipt into the plant. It would be wise to hold any product until you have... 

Gombnstible concentration reduction can also be used to prevent deflagrations and detonations in process equipment and piping. The combustible concentration is reduced below the lower flammable limit (LFL) by means of ventilation (air dilution). 

Regardless of the implementation strategy you select, try to build in at least some degree of local involvement in planning and implementation. Local involvement can give facility personnel "ownership" of the process, meaning that they will be more likely to work to overcome any problems or false starts. In addition, local participation means that you will be able to identify any local barriers to implementation—sooner rather than later. 

Primary emphasis is given to flow through circular pipes or tubes since this is the usual means of movement of gases and liquids in process plants. Flow through duct systems is treated with the fan section of Compression in Volume 3. 

Exposure of coupons or specimens to the process stream cannot be achieved satisfactorily unless they are rigidly supported in a rack, although in some cases it may be possible to simply hang them in by means of a wire. Methods of exposure coupons are described in ASTM Method G4 1984. 

In processes involving whole cells the required product can often be formed in a single step, although the cells essentially carry out a multi-step synthesis. This means that only a single product purification is necessary. Conversely, in chemical synthesis of compounds, each step in the synthesis is usually carried out separately. Thus the product of one reaction must often be purified before it can be used in the next step in the synthetic sequence. This multi-step approach is expensive, time consuming and can require a complex process plant to handle the individual steps on an industrial scale. 

Tank formation means that the cured positive and negative raw plates are inserted alternately in special tanks filled with fairly dilute sulfuric acid (generally in the range 1.1 to 1.15gcm 3) and positive and negative plates are connected, a number of each, in parallel with a rectifier. The formation process means that the active material of the plates is electrochemically transformed into the final stage, namely ... 

The S-S linkage of disulfides and the C-S linkage of certain sulfides can undergo photoinduced homolysis. The low reactivity of the sulfur-centered radicals in addition or abstraction processes means that primary radical termination can be a complication. The disulfides may also be extremely susceptible to transfer to initiator (Ci for 88 is ca 0.5, Sections 6.2.2.2 and 9.3.2). However, these features are used to advantage when the disulfides are used as initiators in the synthesis of tel ec he lies295 or in living radical polymerizations. 96 The most common initiators in this context are the dithiuram disulfides (88) which are both thermal and photochemical initiators. The corresponding monosulfides [e.g. (89)J are thermally stable but can be used as photoinitiators. The chemistry of these initiators is discussed in more detail in Section 9.3.2. 

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