Tapping

In gas analysis the burettes are generally vertical graduated tubes provided with a tap at the upper end. The lower end is connected by means of tubing to a reservoir containing mercury or water, by means of which the pressure on the gas enclosed between the tap and the liquid surface may be adjusted and ascertained. 

Kipp s apparatus Equipment for the production of a gas by interaction of a liquid and a solid. It consists of three receptacles, the top is reservoir for the liquid and is connected to the bottom. The middle contains the solid and a tap for the gas. When gas is released the liquid rises and reacts with the solid, when the tap is closed the back pressure returns the liquid lo the lower reservoir and reaction cease . Once widely used for the production of H.S (HCl and FeS) and C O (HCl and CaC(3,<). 

Beam pumping and electric submersible pumps (ESP) require a source of power. On land it may be convenient to tap into the local electricity network, or in the case of the beam pump to use a diesel powered engine. Offshore (ESP only) provision for power generation must be made to drive down hole electric pumps. 

The water quality (air content) and the water flow influenced the measurements using one channel. Therefore the four channel system was first tested in the laboratory with a stationary tube. The best results were obtained using tap water and a well controlled flow in a water-filled chamber. A great difference in the concentration of air in the different grades of water was obvious, and the tap water was superior to soft water during these measurements. 

Today the coin-tap test is a widely used technique on wind turbine rotor blades for inspection of thin GFRP laminates for disbonded and delaminated areas. However, since the sensitivity of this technique depends not only on the operator but also on the thickness of the inspected component, the coin-tap testing technique is most sensitive to defects positioned near the surface of the laminate. Therefore, there has been an increasing demand for alternative non-destmctive testing techniques which is less operator dependent and also more sensitive to delaminations and disbonded areas situated beyond thicker GFRP-laminates. 

Fig. XVni-2. Successive STM images of (a) Ni(llO) with a chemisorbed layer of oxygen atoms and (b) after exposure to 3 1 of H2S. The area shown in 85 x 91 A. [From F. Besenbacher, P. T. Sprunger, L. Ruan, L. Olesen, I. Stensgaard, and E. Lcegsgaard, Tap. Catal., 1, 325 (1994).]...

Zong Q, inniss D, K]oiier K and Eiings V B 1993 Fractured poiymer/siiica fiber surface studied by tapping mode atomic force microscopy Surf. Sc/. Lett. 290 L688... 

Flansma P K ef a/1994 Tapping mode atomic force microscopy in iiquids Appl. Phys. Lett. 64 1738... 

Dhinojwala A and Granick S 1997 Surface forces In the tapping mode solvent permeability and hydrodynamic thickness of adsorbed polymer brushes Macromoiecuies 30 1079-85... 

Nitric acid is prepared in the laboratory by distilling equal weights of potassium nitrate and concentrated sulphuric acid using an air condenser, the stem of which dips into a flask cooled by tap water. The reaction is ... 

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 . 

When constructing a manometer of the type shown in Fig. 12(c), it is impor tant to apply a very high vacuum (e.g., with a Hy-Vac pump) to the manometer while the mercury in the left-hand (sealed) limb is heated until it boils unless this is done, traces of air will remain in this limb and cause inaccurate readings. During a distillation, the tap I should be kept closed except when a pressure reading is being taken if it is left open indefinitely, a sudden default by the distillation apparatus or by the pump may cause the mercury in the sealed limb of G to fly back and fracture the top of the limb. 

G. A. R. Kon Jour. Chem. Soc.., 1930, 182) described a modification of the Perkin triangle having only two taps instead of the three described above. It may be purchased from Quickfit Quartz, Ltd., Quickfit Woiks, Stone, Staffs. 

The tube is fitted with a two-way tap, so that B can be used for evacuating the tube. 

Add about 0 2 g. of ferrous sulphate crystals to the first portion of the filtrate contained in a boiling-tube. An immediate dark greenish-grey precipitate of ferrous hydroxide should occur if the mixture remains clear, add a few ml. of sodium hydroxide solution. Now boil the mixture gently for a few minutes to ensure formation of the ferrocyanide, cool under the tap, add one drop of ferric chloride solution, and then acidify... 

The air may be collected directly into a Hempel gas-burette (Fig. 76) and there measured. This burette consists of a glass tube H calibrated in ml. from the tap E downwards, and connected by a piece of rubber tubing to the reservoir R, the height of which can be adjusted. The tap E is a 3-way tap. by which the tube H can be connected directly through to the capillary tube above, or either tube can be connected through the left- hand end of the tap to the atmosphere. 

If, on the other hand, the thermometer has previously been used at some temperature below the freezing-point of benzene, when the bulb is originally placed in the beaker of water at 7-8 C., the mercury will rise in the capillary and ultimately collect in the upper part of the reservoir at a. When the expansion is complete, again tap the thermometer sharply at R so that this excess of mercury drops down into b, and then as before check the success of the setting by placing the thermometer m some partly frozen benzene. In either case, if the adjustment is not complete, repeat the operations, making a further small adjustment, until a satisfactory result is obtained. 

Prepare the acetylating mixture by adding i volume of acetic anhydride to 4 volumes of pure anhydrous pyridine, and shaking thoroughly. Immediately before use, transfer the mixture to a clean dry burette having a welUfitting glass tap, and then close the top of the burette by means of a soda-lime tube. 

In filling the tube R, one tap is inserted after being carefully greased with a high-vacuum or silicone grease. The taps are provided with scored grooves (that run completely around them near their outer end) which act as a trap to prevent... 

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