NH4OH

2 HF In the semiconductor manufacturing process, buffered HE (BHF) and DHF are widely used for the etching of oxide layers and the removal of native oxide. Most polished surfaces will have a thin layer of oxide poly-Si, oxide, W, Cu, and so on. The removal of oxide by DHF could also help to remove metallic ions in oxide. DHF cleaning is also known to be very effective in removing particles trapped in recessed and eroded features. 

TABLE 16.2 General Properties of Citric and Oxalic Acids. 

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Tin ll) oxides. Lower tin oxides SnO (white, NH4OH to SnCli solution black, heat on white SnO red), form a complex system. 

For this second reaction Kjgs = 181 x 10" and hence pK, for ammonia solution is 4.75. The entity NHj. H2O is often referred to as ammonium hydroxide, NH4OH, a formula which would imply that either nitrogen has a covalency of five, an impossible arrangement, or that NH4OH existed as the ions NH4 and OH". It is possible to crystallise two hydrates from concentrated ammonia solution but neither of these hydrates is ionic. Hence use of the term ammonium hydroxide is to be discouraged in favour of ammonia solution . 

A solution of 4% aq. H2SO4, (301) was heated to 50"C over 30-60 min. Nitrogen was bubbled through the solution during this time. 4-(Cyano-methyl)phenylhydrazine hydrochloride (1080g, 4.77 mol) was added as a solid to the heated mixture. After it had dissolved, A,A-dimethyl-4,4-dimethoxy-butanamine (965 g, 5.98 mol) was added over a period of 30 min. The mixture was then heated at reflux for 2 h. The reaction mixture was cooled and diluted with portions of 30%o aq. NH4OH (21 total) over 0.5 h at a rate to maintain the temperature at 25-30°C. The product was then extracted into isopropyl acetate (3 x 101). The solution was concentrated to 31 which led to a precipitate which was isolated by filtration and washed with cold isopropyl acetate to give 827.4 g (76%) of product. 

P The yellow precipitate of (NH4)3tP(Mo30io)4] is dissolved in NH4OH, then solution is strongly... 

Ammonium hydroxide, NH4OH—15A the concentrated solution which contains 28% NH3 for 6N 400 mL per liter. 

Ammonium sulfide (colorless), (NH4)2S — saturated pass H2S through 200 mL of concentrated NH4OH in the cold until no more gas is dissolved, add 200 mL NH4OH and dilute with water to a liter the addition of 15 g of sulfur is sufficient to make the poly sulfide. 

Chloride reagent dissolve 1.7 g of AgN03 and 25 g KNO3 in water, add 17 mL of concentrated NH4OH and make up to 1 liter with water. 

For most samples liquid-solid chromatography does not offer any special advantages over liquid-liquid chromatography (LLC). One exception is for the analysis of isomers, where LLC excels. Figure 12.32 shows a typical LSC separation of two amphetamines on a silica column using an 80 20 mixture of methylene chloride and methanol containing 1% NH4OH as a mobile phase. Nonpolar stationary phases, such as charcoal-based absorbents, also may be used. 

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