Water-drop test

Protection against ferrous corrosion by sea water can be assessed by IP 135B in which a mild steel pin is suspended in a mixture of oil and standardised synthetic sea water for 24 h at 60 C. Other tests used include a static water drop test and a... 

Fig. 6.1 Contact angle measurements on silica aerogels using water drop test...

Water drop tests are not very revealing and do not necessarily predict the migration susceptibility of metals in microelectronics under field conditions (1). The reason is that metal migration and dendritic formation depend on the state of the metal surface, whether it is oxidized or not, and on whether the oxide passivates the surface or it dissolves in water. For instance, copper will rarely produce dendrites when it is... 

Equation 3 indicates that the more acidic the electrolyte is, the higher the value of and the harder it is to achieve passivation which requires current values > J . For a water drop test at room temperature (pH 7), is 1.3x1 O A/cm which allows passivation to occur. 

The sodium sulphite solution may also be prepared by dissolving 100 g. of pure (or a corresponding quantity of commercial) sodium hydroxide in about 125 ml. of water, and then diluting to 750 ml. The flask is cooled in running water, a few drops of phenolphthalein indicator are added, and sulphur dioxide passed in until the pink colour just disappears (it is advisable to add a further 1-2 drops of the indicator at this point) and then for 2-3 minutes longer. It is best to remove a sample for test from time to time, dilute with 3-4 volumes of water, and test with I drop of phenolphthalein. 

If an appreciable amount of residue remains, note its colour. Add a few drops of water and test the solution (or suspension) with htmus or with Universal indicator paper. Then add a httle dilute hydrochloric acid and observe whether efiervesceiice occurs and the residue dissolves. Apply a flame test with a platinum wire on the hydrochloric acid solution to determine the metal present. (In rare cases, it may be necessary to subject a solution of the residue to the methods of qualitative inorganic analysis to identify the metal or metals present.) If the flame test indicates sodium, repeat the ignition of the substance on platinum foil. 

Verification of the microbial retention efficiency of the membrane filters may be undertaken using either Hquid or aerosol challenge tests. A Hquid challenge test is more stringent. Furthermore, this test can provide retention information for process conditions such as extreme moisture after sterilization or air entrained with water drops. A Hquid challenge is performed using a protocol similar to that described for Hquid filtration. 

Alcohol holdout tests, which are also used to measure aqueous fluid repeUency, iavolve placing drops of aqueous isopropyl alcohol solutions of concentrations 10, 20,. .. 100 wt % on a fabric surface. The rating for the fabric is based on the most concentrated solution that does not penetrate the fabric ia the specified time frame (3M Water RepeUency Test II, Water/Alcohol Drop Test (41) INDA Standard Test 80.6). 

In the 3M Water/Alcohol Drop Test (41), this test is designed to provide a simple, rapid method to assess the aqueous stain resistance of substrates treated with a protective finish. 

M Water Repelleny Testll, Water/Alcohol Drop Test, 3M Test Methods, 3M, St. Paul, Minn., 1992. 

To detect nitrous acid, a drop of the mixture is diluted with water and tested with starch iodide paper. 

Experiment.—Dissolve 1 c.c. of nitromethane in water and test the solution with litmus paper. Then add some phenolphthalein and, drop by drop from a burette, OliV-sodium hydroxide solution. Before a permanent pink colour develops about 2 c.c. of the alkali will be added—a sign that an acid, aci-nitromethane, H2C NOOH, has been formed from the neutral nitromethane. A small sample of this solution gives with ferric chloride a blood-red colour, characteristic of aci-nitro-compounds. The salts of the oci-compound undergo extensive hydrolysis. This is shown by further addition of 0-1 N-alkali which produces a deep red colour. If 10 c.c. of alkali were added and 5 c.c. of 0-1 JV-hydrochloric acid are now run in the solution is decolorised because the liberated oci-compound restricts the hydrolysis of its salt. But the conversion of H2C N02H into H3C.N02 proceeds so rapidly that the red colour reappears in a few moments. 

Water witb a bigb chloride ion content is not safe to drink. The following process is used to test for the presence of Cl (aq) Dissolve 5.0 g of AgNOs in 500 mL of distilled water. Add 10 drops of the solution to 10 mL of the water being tested, and look for a cloudy white precipitate. 

Park and Li [267] also performed an experimental and numerical study in which a serpentine FF with and without diffusion layers was analyzed (see Figure 4.30). For the case in which a DL was not used, an impermeable plate was placed between the anode and cathode plates in order to perform the pressure drop tests. It was observed that the pressure difference between the two cases was as large as 80% of the pressure drop in the case without the DL. It was also explained that the reason for the large pressure difference between both cases was due to the cross-flow phenomena between adjacent channels through the porous diffusion layer. These researchers also performed the pressure drop tests when the fuel cell was running it was observed that the pressure drops were higher in this case than when the cell was inactive. It was believed that this pressure difference was a result of liquid water blocking reactant flow in either the channels or the DLs. 

Soil Column Tests. In the sand penetration test, a minimal amount of water was used. No consideration was given to the hydrostatic pressure which would occur in nature from a body of surface water. A new soil infiltration test was developed to take this into consideration. This test used a maximum amount of water (200 mL) on a minimum amount of treated soil (10 g) and was restricted only by the dimensions of the laboratory equipment. Our aim was to prepare an hydrophobe for soil which would support water over an extended period of time. Whereas water passed through soil treated with hydrophilic compounds within 8 hr, 2 weeks or more were required for penetration through an hydrophobe-treated soil. In the latter case the water level dropped 6 mm or less each day, showing that the cationic surfactant greatly hindered, but did not completely restrict the passage of water. The tests were usually terminated after 2 weeks, due to the large number of samples to be tested. 

Addn of 25% water decreases sensitivity to drop test. Explodes also on contact with coned acid. It is unstable and decomposes slowly even in the presence of traces of water changing to a greenish color (Ref 3)... 

Properties of Calcium Carbide. (Perform the experiment in a fume cupboard ) Assemble an apparatus (see Fig. 76) and check its tightness. Put one or two small pieces of calcium carbide into the dry Wurtz flask and pour water into the dropping funnel. By adding the water dropwise to the calcium carbide, pass a stream of the gas formed through the apparatus (for what purpose ), then collect the gas in a test tube over water and test it with a burning splinter. What happens Write the equation of the reaction. 

Obtain a sample of mixed lead paint and also one of raw linseed oil. To 20 cc. of the mixed paint in a bottle, add 70 cc. of water in 5-cc. lots, shaking vigorously after each addition. This emulsion will contain about 72 per cent of water, and oil is the external phase, as will be shown by a drop test. 

You may need to play around with the drops for a while in order to see the differing affinities that the bag and wrap have for water. One way to do this is to tape the polymers side by side stretched out on a sturdy piece of cardboard. Tilt the cardboard to various angles, testing for the speed with which water drops roll down the incline on the two surfaces. Ultimately, you should find that the drops roll more slowly on the wrap (polyvinylidene chloride) than on the bag (polyethylene terephthalate). The source of this greater stickiness in the wrap is the fairly large chlorine atoms of the polyvinylidene chloride. 

---