Practical tests

The examination of varnish comprises more particularly practical tests and chemical analysis. 

These consist in testing the vamish to ascertain its applicability to the purpose for which it is intended. To this end it is spread in a thin layer on a smooth metal (tinned iron) or glass surface and allowed to dry in the air. The time necessary for complete drying and the appearance are noted, and the film of vamish tested to ascertain if it adheres well. After some time the film is observed to see if it has cracked or sweated, i.e., become oily to the touch. 

Transparent varnishes are spread over delicately coloured objects to see if the colour remains unchanged. 

To test the durability of a varnish, the latter is spread on a sheet of metal when the film is dry, the metal is heated (e.g.,to ioo°) and then immersed in cold water. If the varnish does not crack when subjected to this treatment several times, it is of good quality. 

Complete analysis of a varnish is often extremely difficult. The difficulties are greatest with oil varnishes, these containing drying oils and resins which have been heated so that their physical and chemical characters (solubility in different solvents, density, colour reactions, iodine, acid and saponification numbers, etc.) are changed. Even with simpler varnishes it is difficult to ascertain if they are prepared from a single resin or from several. Minor difficulties are encountered in the determination of the nature of the volatile solvents, although these are sometimes complex mixtures. 

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This study, carried out with coloured and fluorescent penetrants, is based on french standards NFA 09.520 and NFA 09.521. Some practical tests (removing of penetrant and over-washing) and sensitivity tests have been done for eaeh range of produet. 

The reaction with sodium is by no means an infallible practical test for alcohols since, strictly speaking, it is applicable only to pure anhydrous liquids. Traces of water, present as impurities, would give an initial evolution of hydrogen, but reaction would stop after a time if an alcohol is absent furthermore, certain esters and ketones also evolve hydrogen when treated with sodium (compare Section XI,7,6). It may, however, be assumed that if no hydrogen is evolved in the test, the substance is not an alcohol. 

In the former edition attention was drawn to certain drawbacks which accompanied the study of practical organic chemistry, among which the heavy duty on alcohol and the unsatisfactory nature of the practical tests demanded by public examining bodies were specially emphasised. 

In recent years it has been regarded as somewhat passe to refer to Sir Humphrey Davy in a text on cathodic protection. However, his role in the application of cathodic protection should not be ignored. In 1824 Davy presented a series of papers to the Royal Society in London in which he described how zinc and iron anodes could be used to prevent the corrosion of copper sheathing on the wooden hulls of British naval vessels. His paper shows a considerable intuitive awareness of what are now accepted as the principles of cathodic protection. Several practical tests were made on vessels in harbour and on sea-going ships, including the effect of various current densities on the level of protection of the copper. Davy also considered the use of an impressed current device based on a battery, but did not consider the method to be practicable. 

In the case of the evaporative condenser, the heat is input to the condenser coils, which are kept wet by the spray. The water acts both as a heat transfer medium and an evaporative coolant, and its temperature will vary through the stack of tubes. The overall process is complex and ratings are determined from practical tests on a complete condenser [16]. 

Figure 37. Practical test results of a 2CR5 lithium-manganese dioxide battery in a fully automatic camera at 23 °C.

Develop practical test program to demonstrate components ability to meet structural and performance criteria. Extent of such test program, if any, depends on economic value of component, number of units to be produced, consequences of failure, accuracy of structural analysis and design, margins of safety used in design, knowledge about service loads and environments, and difficulty of duplicating service loads and conditions in test... 

An excellent online quizzing bank in which instructors can easily quiz students using prewritten, multiple-choice questions for each text chapter (not from the test bank). Students receive instant feedback and can take the quizzes multiple times. Instructors can go to a protected Web site to view results by quiz, student, or question, or they can get weekly results by e-mail. Excellent for practice testing or homework or both. 

Many modes of constructing schemes of a particular form can be treated as simplest regularization modes. The canonical form of a scheme is convenient not only for practical tests of stability, but also for proper... 

Friedli D, Kappeler W, Zimmermann, S. Validation of computer system practical testing of a standard LIMS. Pharmaceut Acta Helv 1998 72 343-8. 

F. Practical test for monitoring the allergy-labeling system. 

Correction of labeling by administrative guidance FIGURE 4.5 Outline of the practical test used to monitor the allergy-labeling system. 

Protocols to determine exposure scenarios should require that application be made using normal practices. Test substance application must be thoroughly documented by researchers. Documentation should include weights and volumes of materials added to... 

His experiments were isa successful that h practical test of the efficacy of his methods was made, He wrote, to a friend ... 

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