Special apparatus

A spectrophotometer or a filter photometer at or close to 670 nm is used for the determination. Cuvettes with path lengths of 0.5,1,5 and 10 cm are used depending on the intensity of the colour development. Automatic piston pipettes adjusted to a volume of 0.5 mL are recommended for adding reagents. The absorbance readings should be recalculated according to the path length used for the calibration. 

Samples should be taken from the ordinary hydrocast samplers immediately after the oxygen sample and in the the same manner as these samples (see Chapter 4). The hydrocast samplers should preferably be all-plastic, since sulphide reacts with many metals. When no oxygen is present in the water, samples for hydrogen sulphide determination should be taken first (see also Chapter 2). We use 50 mL oxygen bottles. Hydrogen sulphide is probably present in the water when the manganese hydroxide precipitate in the oxygen sample is completely white instead of brownish. 

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Pure water for use in the laboratory can be obtained from tap water (hard or soft) by distillation if water of great purity is required, distillation must be carried out in special apparatus, usually made of quartz, not glass or metal precautions must be taken to avoid any spray getting into the distillate. Water which is sufficiently pure for most laboratory purposes can, however, be obtained by passing tap water through cation-exchangers and anion-exchangers as described above, when the water is deionised . 

The difficulties of working with small quantities of liquids are much greater than with small quantities of solids. For example a competent worker can, and does in fact, often work with 100 mg, of solid without any special apparatus. With liquids this is often not practicable because of the much greater losses entailed, particularly when it is realised that one ordinary-sized drop weighs about 50-100 mg. The account which follows gives details of modifications of standard apparatus suitable for the semi-micro scale defined above. 

Another important method of following protein hydrolysis is that due to Van Slyke, and consists in estimating the free amino groups liberated by treatment with nitrous acid, whereby gaseous nitrogen is evolved and measured in a special apparatus. 

The reaction is of general application the yields of primary alcohols approach the theoretical values, and for secondary alcohols are 85-95 per cent. The process is best carried out with the aid of a special apparatus. 

A special apparatus (Fig. Ill, 40,1) renders the preparation of iodides from alcohols a very simple operation. The special features of the apparatus are —(i) a wide bored (3-4 mm.) stopcock A which considerably reduces the danger of crystallisation in the bore of the tap of the iodine from the hot alcoholic solution (ii) a reservoir B for the solid iodine and possessing a capacity sufficiently large to hold all the alkyl iodide produced (iii) a wide tube C which permits the alcohol vapour fix)m the flask D to pass rapidly into the reservoir B, thus ensuring that the iodine is dissolved by alcohol which is almost at the boiling point. An improved apparatus is shown in Fig. Ill, 40, 2, a and b here a... 

If the apparatus of Fig. Ill, 40, 2 is employed, the iodide is removed by suitably turning the three-way stopcock. It is then, of course, unnecessary to discoimect the special apparatus from the flask. 

Ethyl bromoacetate (1). Fit a large modified Dean and Stark apparatus provided with a stopcock at the lower end (a convenient size is shown in Fig. Ill, 126, 1) to the 1-htre flask containing the crude bromoacetic acid of the previous preparation and attach a double surface condenser to the upper end. Mix the acid with 155 ml. of absolute ethyl alcohol, 240 ml. of sodium-dried benzene and 1 ml. of concentrated sulphuric acid. Heat the flask on a water bath water, benzene and alcohol will collect in the special apparatus and separate into two layers, the lower layer consisting of approximately 50 per cent, alcohol. Run ofi the lower layer (ca. 75 ml.), which includes all the water formed in the... 

If a small-scale special apparatus is not available, proceed as follows Place 1-5 g. (1-9 ml.) of re-butyl alcohol and 0 28 g. of purified red phosphorus in a 25 ml. round-bottomed flask, and add 2-5 g. of io ne in 2 portions. Allow to stand for 2-3 minutes, heat on a boiling water bath under reflux for 30 minutes, add 5 ml. of water and distil. Separate the lower layer of the distillate. Work up the product as described in 111,40. 

The methods in which iodine is used as a catalyst for the reaction between ceric sulfate and nitrite or arsenite (86,87) are capable of determining smaH amounts of iodine. However, these catalytic methods are deHcate and require accurate timing, carefiH temperature control, and special apparatus. 

The second parameter, tear strength, describes the film resistance to tear propagation. It is measured with a special apparatus, the Ehnendorf Tear Tester (ASTM D1922), and defined as the weight of a loaded pendulum capable of tearing a notched piece of film. Two values are usually measured for each film sample. One determines tear propagation in the machine direction of the film, the other in the transverse direction. 

Dispersion Stability of Disperse Dyes at High Temperature. A disperse dye dyebath is treated under the desired test conditions at 130°C in a special apparatus (Gaston County Lab Dye and Chemical Tester) and filtered through cotton and polyester filters. The filter with the heaviest residue is then compared with a series of standard photographs of standard performance and rated equal to the one it most resembles (1 poor, 5 excellent). 

Photochemical [2 + 2] cycloaddition is a powerful way to produce cyclobutanes, which, in turn, are reactive synthesis intermediates. N-Methylpyrrole adds aldehydes via [2 -I- 2] photocycloaddition to give transient oxetanes with high regioselectivity Ring-opening produces 3-(oi-hydroxyalkyl)pyrroles which are oxidized easily to 3-arylpyrroles, such as 3-BUTYROYL-l-METHYL-PYRROLE. With a special apparatus, ethylene is conveniently added to 3-methyl-... 

Nickel (II) phthalocyanine [14055-02-8] M 571,3, m >300 , Wash well with H2O and boiling EtOH and sublime at high vacuum in a slight stream of C02. A special apparatus is used (see reference) with the phthallocyanine being heated to red heat. The sublimate is made of needles with an extremely bright red lustre. The powder is dull greenish blue in colour. [J Chem Soc 1719 7936.]... 

Recently, the parent A -halomethylpyridinium halides 7a, 7b, and 7f-7i (X-CH2-Py X , X = Cl, Br) have been synthesized with yields up to 90% by treating a mixture of an equimolar amount of SOX2 (X = Cl, Br) and the corresponding pyridine with gaseous formaldehyde in CH2CI2 or MeCN at 0°C. Tire formaldehyde was generated externally from paraformaldehyde in a special apparatus (99JOC3113). 

Broken bit components left behind in a borehole when the drillstring is removed and hand tools and other foreign objects falling in the borehole constitute Junk that must be retrieved. These components cannot be drilled up during normal drilling operations. They may be milled with metal drilling bits and other special apparatus that can eventually remove these items in pieces. Such Junk items can be very difficult to remove. 

Since, however, density is affected to a considerable degree by temperature, and since its accurate measurement demands special apparatus and great care, it is not a reliable measure of the strength of sea water. 

Excellent yields are obtained by treating methyl sulfate with potassium iodide, and no special apparatus is required. 

The information content of AV and AS is similar. Values of AV are usually more precise than those of AS, although they require specialized apparatus for their measurement. If ions are being formed in the activation step, AV may be -20 cm3 mol-1. This effect reflects the electrostriction of the solvent. If the transition state features bond breaking, as in an SnI reaction, AV 10 cm3 mol-1. Conversely, AV -10 cm3 mol-1 is characteristic of bond making. 

Two-phase titration is an old but very good method requiring no special apparatus [50]. 

Removal of solid debris using a micro-centrifuge is an alternative technique to filtration. Although it requires special apparatus, the... 

Carbon dioxide can be liquefied under high pressure (supercritical CO2). Several reactions have been done using supercritical CO2 as the medium, but special apparatus is required. This medium offers many advantages," and some disadvantages, but is an interesting new area of research. 

Essential oil components 800-900 C Induction of fluorescence in a special apparatus. [18]... 

This index is divided into two parts. Part 1 gives the names of compounds as used in these volumes as well as general terms for classes of compounds, types of reactions, synthetic applications, special apparatus, and unfamiliar methods. The complete names of all specific compounds are given in normal order as written in the text (e.g., ethyl cyano-acetate appears under ethyl). Some entries are common names and others are systematic Chemical Abstracts names, whichever was used in the text. 

Carotenoids with ally lie hydroxy and keto groups such as the 3-hydroxy-4-keto group in astaxanthin which is widespread in marine animals, microorganisms, and algae undergo oxidation in the presence of alkali and air. Eor such samples, saponification is not recommended or must be carried out under anaerobic conditions. Eor this purpose, a special apparatus and procedure were developed by Schiedt et al. ... 

We have studied the steady-state kinetics and selectivity of this reaction on clean, well-characterized sinxle-crystal surfaces of silver by usinx a special apparatus which allows rapid ( 20 s) transfer between a hixh-pressure catalytic microreactor and an ultra-hixh vacuum surface analysis (AES, XPS, LEED, TDS) chamber. The results of some of our recent studies of this reaction will be reviewed. These sinxle-crystal studies have provided considerable new insixht into the reaction pathway throuxh molecularly adsorbed O2 and C2H4, the structural sensitivity of real silver catalysts, and the role of chlorine adatoms in pro-motinx catalyst selectivity via an ensemble effect. 

Internal or external mobilities in additive binary systems provide more heuristic information than in pure salts. For pure salts, the only parameter that can be obtained easily is the temperature, while detecting a change in pressure needs a difficult technique as well as specialized apparatus. However, in additive binary systems, where the composition can be easily varied, two mobilities can be compared under the same condition. 

Some processes have been known and investigated for a long time, even over decades, but are not used for industrial production or even for common laboratory-scale practice. Although promising, safety reasons may restrict widespread permission to use them or render them inconvenient. The processes are investigated but at extreme dilution or in complex special apparatus. 

Fit up the assembly depicted in Fig. Ill, 40, 1 insert a plug of glass wool at the bottom of B (just above the wide bore tap A). i> is a 100 ml. bolt-head flask, B has a capacity of about 30 ml. (1) and is a Liebig (but may be a double smface) condenser. Place 16 g. (19 ml.) of n-butyl alcohol and 2-75 g. of purified red phosphorus (Section II,50,J) in the flask and 25 g. of iodine in the special apparatus. Make sure that all the corks fit tightly and do not leak. Heat the flask gently on a wire... 

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