Sulfates and silicon

Sodium Sulfate Mixed with Rare Earth Sulfates and Silicon Dioxide... 

A new solid state chemical sensor for sulfur dioxide utilizing a sodium sulfate/rare earth sulfates/silicon dioxide electrolyte has been developed. The addition of rare earth sulfates and silicon dioxide to the sodium sulfate electrolyte was found to enhance the durability and electrical conductivity of the electrolyte. The electrolyte exhibits a Nernstian response in the range of SC gas concentrations from 30 ppm to 1 %. 

Shiokawa, 1985b, J. Electrochan. Soc. 132,2519. Imanaka, N., G. Adachi and J. Shiokawa, 1986a, A solid electrolyte for sulfur dioxide detection, sodium sulfate mixed with rare earth sulfates and silicon dioxide, ACS Symposium on Chemical Sensors -Fundamentals and Applications (American Chemical Society) p. 121. 

The luminescence of macrocrystalline cadmium and zinc sulfides has been studied very thoroughly The colloidal solutions of these compounds also fluoresce, the intensity and wavelengths of emission depending on how the colloids were prepared. We will divide the description of the fluorescence phenomena into two parts. In this section we will discuss the fluorescence of larger colloidal particles, i.e. of CdS particles which are yellow as the macrocrystalline material, and of ZnS particles whose absorption spectrum also resembles that of the macrocrystals. These colloids are obtained by precipitating CdS or ZnS in the presence of the silicon dioxide stabilizer mentioned in Sect. 3.2, or in the presence of 10 M sodium polyphosphate , or surfactants such as sodium dodecyl sulfate and cetyldimethylbenzyl-ammonium... 

The bomb method for sulfur determination (ASTM D129) uses sample combustion in oxygen and conversion of the sulfur to barium sulfate, which is determined by mass. This method is suitable for samples containing 0.1 to 5.0% w/w sulfur and can be used for most low-volatility petroleum products. Elements that produce residues insoluble in hydrochloric acid interfere with this method this includes aluminum, calcium, iron, lead, and silicon, plus minerals such as asbestos, mica, and silica, and an alternative method (ASTM D1552) is preferred. This method describes three procedures the sample is first pyrolyzed in either an induction furnace or a resistance furnace the sulfur is then converted to sulfur dioxide, and the sulfur dioxide is either titrated with potassium iodate-starch reagent or is analyzed by infrared spectroscopy. This method is generally suitable for samples containing from 0.06 to 8.0% w/w sulfur that distill at temperatures above 177°C (351°F). 

Aluminum is the third most abundant element found in the Earths crust. It is found in concentrations of 83,200 ppm (parts-per-million) in the crust. Only the nonmetals oxygen and silicon are found in greater abundance. Aluminum oxide (Al Oj) is the fourth most abundant compound found on Earth, with a weight of 69,900 ppm. Another alum-type compound is potassium aluminum sulfate [KA1(S0 )2 12H20]. Although aluminum is not found in its free metalhc state, it is the most widely distributed metal (in compound form) on Earth. Aluminum is also the most abundant element found on the moon. 

Studies of the formation, chemical composition, and properties of deposits have shown that they consist of partially oxidized organic material, including more or less nitrogen, sulfur, and phosphorus. Compounds of iron, silicon, calcium, and other metals are present in small quantity, together with substantial amounts of lead oxides, sulfates, and halides from combustion of the antiknock fluid. The effects of these deposits are both physical and chemical in nature they may physically interfere with lubrication, heat transfer, gas flow, operation of valves and spark plugs chemically, they may bring about corrosion and oxidation. 

In our investigation, sodium sulfate was selected as the electrolyte. Rare earth sulfates Lj CSO, (LnsY and Gd) were added in order to increase the electrical conductivity. Silicon dioxide was ad ed so as to obtain the network structure which is effective for Na cation conduction and to prevent the electrolyte from becoming too soft. A thinner electrolyte was possible to prepare by mixing in SiC. The suppression of the phase transformation(15, 16) from Na2S0,-I(a high temperature phase) to Na2S0 -IH(a low temperature phase was also achieved by mixing rare earth sulfates(Ln=Y and Gd) and silicon dioxide into sodium sulfate. 

In conclusion, the sodium sulfate mixed with rare earth sulfates (Ln=Y and Gd) and silicon dioxide exhibits high electrical conductivity and is more durable than the pure sodium sulfate. Furthermore, the Na-SO, -Y (S0, -SiO solid electrolyte ipaintains a similar phase to Na-oO -I, whicn is excellent in Na+ cation conduction. The measured EMf was in excellent accordance with the calculated EMF, at SO2 gas concentration in the range of 30 ppm to 1 %. In fact, the solid reference electrode method could be applicable as a practical SO2 gas detector. 

Fusion with anhydrous potassium fluoride in a platinum dish is undoubtedly the simplest, most effective and reliable method available for the complete dissolution of a wide variety of siliceous materials. The potassium fluoride cake can then be transposed in the same container to a pyrosulfate fusion with rapid and complete volatilisation of both hydrogen fluoride and silicon tetrafluoride [54]. Except for a small quantity of barium sulfate, the pyrosulfate cake will dissolve completely in dilute hydrochloric acid. The resulting pyrosulfate fusion is one of the simplest and most effective methods available for rapid, complete and dependable dissolution of nonsiliceous materials, particularly high-fired oxides. This fusion has the distinct advantage that the flux can be obtained by simply adding easily purified alkali metal sulfates to sulfuric acid, and the fusion can be carried out in either borosilicate flasks or platinum vessels with very little contamination from either reagents or containers. 

Organic substances such as methane, naphthalene, and sucrose, and inorganic substances such as iodine, sulfur trioxide, carbon dioxide, and ice are molecular solids. Salts such as sodium chloride, potassium nitrate, and magnesium sulfate have ionic bonding structures. All metal elements, such as copper, silver, and iron, have metallic bonds. Examples of covalent network solids are diamond, graphite, and silicon dioxide. 

Aluminum is present in many primary minerals. The weathering of these primary minerals over time results in the deposition of sedimentary clay minerals, such as the aluminosilicates kaolinite and montmorillonite. The weathering of soil results in the more rapid release of silicon, and aluminum precipitates as hydrated aluminum oxides such as gibbsite and boehmite, which are constituents of bauxites and laterites (Bodek et al. 1988). Aluminum is found in the soil complexed with other electron rich species such as fluoride, sulfate, and phosphate. 

Spectrophotometric techniques based on molecular absorption radiation for determining nutrients (NO3, N02, NII4, N2, phosphorus, and silicon) as well as chlorine, fluoride, cyanide, sulfate, and sulfide. 

Secondary amines give the aminosilane, with the more hindered amines requiring heating under pressure. With primary amines, the aminosilane is formed initially, but the size of the substituents at nitrogen and silicon determines whether deamination subsequently occurs. Prolonged heating under reflux in the presence of ammonium sulfate, or the precipitated amine hydrochloride as acid catalyst yields the disilazane in good yield. 

The silica gel column was eluted starting with hexane (70 mL), followed by 2% ethyl acetate/hexane (100 mL) 5% ethyl acetate/hexane (100 mL) 10% ethyl acetate/hexane (600 mL). The fractions were monitored with 20% ethyl acetate/hexane, using silicon 7 GF plates (purchased from Analtech, Inc.), thickness 250 xm, 20 cm long x 5 cm wide. The plates were sprayed with 3% ceric sulfate and heated at 350°C to detect dienone and monoenone. Alternatively, silica gel 60 F-254 plates (purchased from EM Laboratories, Inc.), thickness 25 mm, 20 cm long x 5 cm wide may be used. Detection may be made with ultraviolet light. The ratio of 1 g of crude dienone to 15 g of silica gel is adequate for obtaining pure spiro[5.7]trideca-l,4-dien 3 one. 

Many of the interelement interferences result from the formation of refractory compounds such as the interference of phosphorous, sulfate, and aluminum with the determination of calcium and the interference of silicon with the determination of aluminum, calcium, and many other elements. Usually these interferences can be overcome by using an acetylene-nitrous oxide flame rather than an acetylene-air flame, although silicon still interferes with the determination of aluminum. Since the use of the nitrous oxide flame usually results in lower sensitivity, releasing agents such as lanthanum and strontium and complexing agents such as EDTA are used frequently to overcome many of the interferences of this type. Details may be found in the manuals and standard reference works on AAS. Since silicon is one of the worst offenders, the use of an HF procedure is preferable when at all possible. 

Of course, once the ore is obtained from its deposit, the actual work of extracting the desired metal has yet to be accomplished. In addition to metals, a variety of other substances comprise natural minerals. Since aluminum and silicon are the most prevalent elements in the Earth s crust, most of the metals exist naturally as aluminates, silicates, or aluminosilicates. The most common minerals are feldspars and clays. These materials have been used since ancient times for the production of materials such as pottery, brick, and china. An example of a feldspar is K2Al2Si60i6, which corresponds to a mixture of potassium superoxide, alumina, and silica (K20-Al203 6Si02). Upon contact with water and carbon dioxide, a weathering reaction results in kaolinite, an aluminosilicate clay (Eq. 1). However, in addition to these oxidized sources of metals, there are substances such as alkaline carbonates, sulfates, phosphates, as well as organic matter that need to be removed to yield the desired metal. As you would expect, the yield for this process is quite low ores typically possess less than 1 % of the desired metal ... 

Lipopeptldes emulsify with difficulty aromatic oils such as styrene or toluene. Furthermore they are not able to emulsify some oils such as vaseline, ricin, wheat germ and silicon oils. To emulsify such oils we have used a binary emulsifying system consisting of a mixture of a fatty alcohol (cetyl alcohol) and a ionic lipopeptide (liposarcosine chlorhydrate, lipolysine bromhydrate or llpoglutamic acid sodium salt). With concentrations of lipopeptide and cetyl alcohol of 1 to 3 % we have obtained miniemulsions similar to those obtained by El Aasser and al. with sodium lauryl sulfate and cetyl alcohol (10). 

The chemicals may constitute a substantial portion of the finished textile. In many cases 10% or more of the fabric s final weight may derive from textile chemicals added to improve or enhance one or another of the fabric s properties. Representative raw materials employed for textile finishing applications are fatty alcohol ether sulfates, vinyl acetate-ethylene copolymers, hydrated alumina, alkylolamides, alkoxylates, chlorinated paraffins, alginates, sodium tripolyphosphates, sorbitan fatty acid esters, ethoxylated triglycerides, and silicones. 

Magnesium trisilicate hydrate (Mg2Si30s xH20, CAS No. 39365-87-2) is constituted of magnesium oxide and silicon dioxide with varying proportions of water. It should contain not less than 20% of magnesium oxide and not less than 45% of silicon dioxide and can be prepared from sodium silicate and magnesium sulfate. It also occurs in nature as the minerals meerschaum, parasepiolite, and sepiolite. 

---