Plasmas at the surface of or inside liquids are of importance for emerging applications, and are often formed with stagnant liquids. Here, the authors present the generation of a direct-current, atmospheric-pressure microplasma at the surface of a liquid water microjet that enables solution species to be transported by forced convection. The water jet is formed by pumping conductive ionic solutions through a plastic capillary tube in a vertically falling geometry, and overcomes Plateau–Rayleigh instabilities by controlling the flow rate, resulting in a constant diameter jet of ∼0.45 mm over lengths of more than 30 mm. Analysis of the electrical characteristics of the complete microplasma-water jet system shows that the current–voltage (I-V) relationship is linear with a large positive slope when the solution conductivity is relatively low. The authors show that the primary contribution to this large resistance is the confined solution geometry. As proof-of-concept, the authors demonstrate that plasmonic Ag nanoparticles can be continuously produced at steady state from solutions of silver nitrate, opening up the possibility of scaled-up production of materials by plasma-liquid processes.

A method, together with a modilication for obtaining high sensitivity, is described for determining the "reactive" silicon content of water; it is based on the absorptiometric measurement of solutions of reduced 8-molybdosilicic acid. The within-batch coefficient of variation of the optical-density difference, optical density of sample less optical density of reagent blank solution, varied from 7 per cent. to 0-2 per cent. for concentrations of 0.01 and 0.5 p.p.m. of silica, respectively. The limit of detection was about 0.001 p.p.m. of silica. The effects caused by several other substances have been determined. The analysis time is about 14 hours for a batch of 10 samples in duplicate.* "Reactive" silicon is defined in this paper as those forms of silicon-mainly monomeric and dimeric silicic acid-that react with ammonium molybclate in 10 minutes under the conditions of the method given in this paper.

The effect of experimental conditions on the formation, stability (in the presence of reagents used for destroying molybdophosphoric acid) and reduction of a-and p-molybdosilicic acids -has been determined. The effectiveness of several reagents for preventing inierference from phosphate has also been investigated. Both cr-molybdosilicic: acid reduced by stannous tin and p-molybdosilicic acid reduced by 1 -amino-2-naphthol-4-sulphonic acid, should be suitable for precise methods of determining "reactive" silicon in water.AT the steam pressures and temperatures used in modern power stations, silicic acid is appreciably soluble in steam, The concentration of silicon in boiler and make-up water is therefore controlled to ensure that the steam contains not more than about 0.02 p.p.m. of silica; above about 0.02 to 0.04 p.p.m. of silica undesirable deposits may be formed on turbine blades.Methods are therefore needed for deteirmining both the "reactive"* and total silicon concentrations in a range of aqueous samples from steamwater circuits in power stations.Thus the methods must be suitable for conde:nsate, feed-water and steam (0-002 to 0-05 p.p.m. of silica), make-up water (0.005 to 0-2 p.p.rrt. of silica) and boiler water (0.2 to 75 p.p.m. of silica).The ratio of phosphate (p.p.m.) to silica (p.p.m.) is usually between 0 and 20, but occasionally ratios as high as 50 may occur.The methods must also be precise, so that they can be used for determining small amounts of "non-reactive" silicon as the difference between the total and "reactive" silicon contents.Absorptiometric methods in which the reduced aand P-molybdosilicic acids are used appear to be the only sufficiently sensitive means of determining extremely small concentrations of silicic acid. They can also be used for determining total silicon provided all forms of silicon are converted to silicate or monomeric silicic acid in an earlier step.This paper reports an investigation of the molybdosilicic acids to determine suitable conditions for each method; Parts 112 and 1113 give details of the methods and the results obtained.Two forms of molybdosilicic acid, a-and p-, are of analytical interest and were first distinguished by S t r i ~k l a n d . ~Each form can be reduced to several different blue compounds with various reducing agents, and Strickland4 has determined the properties of several forms and the conditions for their formation. The relative amounts of ci-and P-molybdosilicic acids produced and their stabilities appear to be affected by factors such as the concentrations of acids, molybdate, neutral salts and reagents such as oxalic or tartaric acid used for destroying molybdophosphoric acid. However, the literature does not give quantitative values for all these effects, and they have, therefore, been investigated.Boiler waters often also contain added phosphate. EXPERIMENTAL APPARATUS, REAGENTS AND TECHNIQUE-All optical-density measurements were made in 4-cm cuvettes with a Hilger Cvispek spectrophotometer against distilled water in the reference cu...

For details of earlier parts of this series, see reference list, p. 61. t "Reactive" silicon (mainly monomeric and dimeric silicic acid) is defined in this paper as those forms of silicon which react with ammonium molybdate in 10 minutes to form molybdosilicic acid under the conditions of the method given in Part IV of this series.*

A method is described for determining the total silicon content of water a t low concentrations. I t consists in evaporation and subsequent fusion of samples with sodium carbonate ; the resulting sodium silicate is determined absorptiometrically as reduced or-molybdosilicic acid. The absorptiometric procedure is precise, and the major errors, a t low concentrations, arise in the fusion procedure. The standard deviation, for samples between 2 and 20 ml, was about 0.3 p g of silica over the range 0 to 60 pg of silica. Four samples can be analysed in duplicate per day.t "Reactive" silicon-mainly monomeric and dimeric silicic acid-is defined in this paper as those forms of silicon that react with ammonium molybdate in 10 minutes to form molybdosilicic acid under the conditions of the method given in Part I1 of this series.' * The entire procedure was carried out.