Aqueous liquid, penetration

Hoyland (2) contends that aqueous liquids penetrate paper more by this process than by capillary action. Commencing with Fick s second law of diffusion which relates the diffusion coefficient D to a function of the concentration change of diffusing liquid in time t at any point x along the direction of diffusion ... 

Aqueous standard solutions are a source of certain difficulties In electrothermal atomic absorption spectrometry of trace metals In biological fluids The viscosities and surface tensions of aqueous standard solutions are substantially less than the viscosities and surface tensions of serum, blood and other proteln-contalnlng fluids These factors Introduce volumetric disparities In pipetting of standard solutions and body fluids, and also cause differences In penetration of these liquids Into porous graphite tubes or rods Preliminary treatment of porous graphite with xylene may help to minimize the differences of liquid penetration (53,67) A more satisfactory solution of this problem Is preparation of standards In aqueous solutions of metal-free dextran (50-60 g/llter), as first proposed by Pekarek et al ( ) for the standardization of serum chromium analyses This practice has been used successfully by the present author for standardization of analyses of serum nickel The standard solutions which are prepared In aqueous dextran resemble serum In regard to viscosity and surface tension Introduction of dextran-contalnlng standard solutions Is an Important contribution to electrothermal atomic absorption analysis of trace metals In body fluids. 

The permeability of concrete to aqueous liquids is reduced by most air entraining agents [35] and this is illustrated in terms of the depth of penetration of water under a pressure of 8 N mm 2 m 48 h in Fig. 3.31. This is reflected in an improved resistance to attack by sulfate-bearing solutions which is indicated by the loss in ultrasonic wave velocity, as shown in Fig. 3.32 [37]. 

Another typical property of cellulose and its derivatives dependent on water sorption is the swelling of the fibre that occurs under the influence of certain solutions such as aqueous sodium hydroxide or an ammoniacal solution of cupric oxide, i.e. cuprammonium . The process of swelling does not start with sorption as in the instance of water. In the first stage of swelling the liquid penetrates the molecular chains of the cellulose, gradually coming in contact with all of them so that chemical combination takes place to form alkali celluloses, (C6H,0O5) NaOH and (C6H,0O5)2 NaOH. 

In this article we report some experimental studies on spreading and penetration of an aqueous IJ ink on a variety of commercial printing papers. The data are tested against existing simple theoretical models for liquid penetration in porous media. No attempt has been made to develop or employ more rigorous models. 

Hoyland arrived at the following solution of [9], to describe penetration of an aqueous liquid by diffusion... 

Alternatively on the basis of a diffusion type model, approximate values of the diffusion coefficient D, have been calculated for these systems. Values of D which fall in the range of 10-2 to 10-5mm/sec are of the same order of magnitude as those obtained by Hoyland (2) for the penetration of various aqueous liquids in bleached softwood paper. Although Hoyland s diffusion model takes into consideration fibre swelling during penetration it still overlooks many of the aforementioned structural complications unique to paper. 

A large excess volume of fixative is important to ensure an effective concentration of fixative is maintained. In some cases, addition of a small amount of detergent (e.g., 0.05%, v/v, Triton X-100) to the fixative as a wetting agent is recommended. This will assist the penetration of the fixative, especially in insects in which such structures as the tracheoles are hydrophobic and, thus, normally exclude the entry of aqueous liquids. 

Given the intrinsic hydrophylic character of cellulose fibres, specific additives are introduced into most papws to reduce this tendency to diffoent extents according to their specific use, for exairple, to minimize the penetration of aqueous liquids, or the excessive wetting associated with certain printing processes [47]. This partial hydrophobization... 

The diagnostic polymers used in the non-aqueous coatings are "hydrogel" in nature and are fully wetted by blood almost instantaneously. Microscopic dye penetration experiments have shown that the liquid penetrates the polymer as well as the coatings in less than 2 s. The generated colors remain stable immediately after reaction and also for an extended time. 

The purpose of sizing is to modify the surface of the fibers to control penetration of aqueous liquids into the paper. The penetration usually correlates with the absorbency, repellency (hydrophobic ty), and spreading of the aqueous liquid concerned. Control of these important properties may be required for three purposes ... 

The principal advantage of the melt-blown process is that it can make fine filaments and produce very light weight fabrics with excellent uniformity. The result is a soft fabric with excellent barrier properties, meaning effective filtration characteristics and resistance to penetration by aqueous liquids. This property is vital in medical applications as concerns on blood-borne diseases increase. 

Most electrode materials are hydrophilic and readily wetted by aqueous solutions. Two methods are used to create and maintain an optimum gas/solution ratio in the electrode. The first method employs a certain excess gas pressure in the gas space. This causes the liquid to be displaced from the wider pores in finer pores the liquid continues to be retained by capillary forces. The second method employs partial wetproofing of tfie electrode by the introduction of hydrophobic materials (e.g., fine PTFE particles). Tfien the electrolyte will penetrate only those pores in the hydrophilic electrode material where the concentration of hydrophobic particles is low. 

These results have been initially considered as evidence for specific ion adsorption at ITIES [71,72]. Its origin was ascribed to extensive ion pair formation between ions in the aqueous phase and ions in the organic phase [71] [cf. Eq. (20)], or to a penetration into the interfacial region [72]. The former model, which has been considered in this context earlier [60], allows one to interpret the enhanced capacity in terms of Eq. (22). Pereira et al. (74) presented more experimental data demonstrating the effect of electrolytes and proposed a simple model, which is based on the lattice-gas model of the liquid liquid interface [23]. Theoretical calculations showed that ion pairing can lead to an increase in the stored... 

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