H2SO4 at

Aminothiazole is efficiently purified by treating an aqueous solution of 2-aminothiazole hydrochloride with H2SO4 at 25 to 105°C, filtering the precipitated reaction product and transforming it back to 2-aminothiazole... 

The resulting acid can often be concentrated to 93—96% H2SO4 at the nitration plant. When the waste acid contains large amounts of dissolved organics, as occurs in a few nitration plants, the acid is then often converted at high temperatures, in the presence of air, to mainly SO2 plus carbon oxides. The SO2 is then oxidi2ed to SO and converted back to concentrated H2SO4. 

Processes. Toluene is nitrated ia two stages. Mononitration occurs ia mixed acid, 30% HNO and 55% H2SO4, at 30—70°C ia a series of continuous stirred-tank reactors. Heat is Hberated and must be removed. The isomer distribution is approximately 58% o-nitrotoluene 38% -nitrotoluene, and 4% y -nitrotoluene (Fig. 1). 

Fig. 14. Heat of mixing of sulfuric acid from H2O and H2SO4 at 25°C (83). To convert to cal, divide by 4.184.

Titanium corrodes very rapidly in acid fluoride environments. It is attacked in boiling HCl or H2SO4 at acid concentrations of >1% or in ca 10 wt % acid concentration at room temperature. Titanium is also attacked by hot caustic solutions, phosphoric acid solutions (concentrations >25 wt%), boiling AlCl (concentrations >10 wt %), dry chlorine gas, anhydrous ammonia above 150°C, and dry hydrogen—dihydrogen sulfide above 150°C. 

Dimethylphenol [95-65-8] M 122.2, m 65°, b 225°/757mm, pK 10.36. Heated with an equal weight of cone H2SO4 at 103-105° for 2-3h, then diluted with four volumes of water, refluxed for Ih, and either steam distd or extracted repeatedly with diethyl ether after cooling to room temperature. The steam distillate was also extracted and evaporated to dryness. (The purification process depends on the much slower sulfonation of 3,5-dimethylphenol than most of its likely contaminants.). It can also be crystd from water, hexane or pet ether, and vacuum sublimed. [Kester Ind Eng Chem (Anal Ed) 24 770 1932 Bernasconi and Paschalis J Am Chem Soc 108 29691986.]... 

Thiourea [62-56-6] M 76.1, m 179 , pK -1.19 (aq H2SO4). Crystd from absolute EtOH, MeOH, acetonitrile or water. Dried under vacuum over H2SO4 at room temperature. 

Acetylenedicarboxylic acid monopotassium salt [928-04-1] M 152.2. Very soluble in H2O, but can be crystd from small volume of H2O in small crystals. These are washed with EtOH and dried over H2SO4 at 125°. [Chem Ber 10 841 1877, Justus Liebigs Ann Chem 272 133 1893.]... 

In addition, the reactions occurring at the impressed current cathode should be heeded. As an example. Fig. 21-7 shows the electrochemical behavior of a stainless steel in flowing 98% H2SO4 at various temperatures. The passivating current density and the protection current requirement increase with increased temperature, while the passive range narrows. Preliminary assessments for a potential-controlled installation can be deduced from such curves. 

The isolation of zinc, over 90% of which is from sulfide ores, depends on conventional physical concentration of the ore by sedimentation or flotation techniques. This is followed by roasting to produce the oxides the SO2 which is generated is used to produce sulfuric acid. The ZnO is then either treated electrolytically or smelted with coke. In the former case the zinc is leached from the crude ZnO with dil H2SO4, at which point cadmium is precipitated by the addition of zinc dust. The ZnS04 solution is then electrolysed and the metal deposited — in a state of 99.95% purity — on to aluminium cathodes. 

The treatment of 8-hydroxy-11-isopr opoxy-7,8,9,10-tetrahydropyr-ido[l,2-A][l,2]benzothiazin-10-ones 42 with eone. H2SO4 at ambient temperature yielded 7,10,10n,ll-tetrahydropyrido[l,2-A][l,2]benzothiazin-9,10-diones 40 (67JMC223, 68USP3408347). 

Amino-6,6n,7,8,910-hexahydropyrido[2,l-c][l,4]benzoxazine was reacted with ethyl 4,4,4-trifluoroacetoacetate in boiling benzene for 12-16 h, then the reaction mixture was concentrated in vacuo and the residue was treated with cone. H2SO4 at 100°C to give tetracyclic 11-trifluoromethyl-l,2,3,4,4a,5,8,9-octahydropyrido[l, 2 4,5][l,4]oxazino[3,2-a]quinolin-9-one in 30% yield (OlMIPl). 

Praziquantel (9) was prepared by the cyclization of 4-cyclohexylcarbonyl-l-phenethyl-2-oxo-l,2,3,4-tetrahydropyrazine in cone. H2SO4 at room temperature in quantitative yield (98H(48)2279). 

Initialiy, 4-bromobenzyl-cyanide is reacted with sodium amide and 2-chloropyridine to give bromophenyl-pyridyl acetonitrile. This is then reacted with sodium amide then dimethyi amino ethyl chloride to give 4.bromophenyl-dimethylamlnoethyl-pyrldyi acetonitrlie. This intermediate is then hydrolyzed and decarboxylated to bromphenirame using 80% H2SO4 at 140°-150°C for 24 hours. The brompheniramine maieate may be made by reaction with maleic acid in ethanol followed by recrystallization from pentanoi. 

The acid-catalyzed hydration of isobutylene produces ter-butyl alcohol. The reaction occurs in the liquid phase in the presence of 50-65% H2SO4 at mild temperatures (10-30°C). The yield is approximately 95% ... 

Fig. 2.5 Corrosion rate of a copper rotating disc in air-saturated 0-1 n H2SO4 at various temperatures (after Zembura )...

Fig. 3.36 Effect of nickel on the anodic behaviour of iron alloys in 1 N H2SO4 at 25°C. Curve 1 Fe curve 2 Fe-lONi Curve 4 Ni (after Beauchamp )...

Fig. 3.39 Weight loss for cast iron exposed in 70% H2SO4 at 130°C for 16 h (after Graham...

Fig. 3.72 Average corrosion rates of amorphous Fe-10Cr-10B-7A and Fe-10Cr-13P-7A alloys in 0 -1 N H2SO4 at 30°C, where X is one of the metalloids indicated on the abscissa ...

Fig. 4,27 Anodic behaviour of Ni-Cu alloys in 10% H2SO4 at ambient temperature. 1, Ni 2, Alloy 400 3, Alloy K500 solution treated 4, Alloy K500 aged (after Flint and...

General corrosion occurs in the weld metal and HAZ of welded Zr-2.25 Nb alloys in an environment of H2SO4 at temperatures greater than 343 K, the rate increasing with concentration. Above 70< oH2S04 both general corrosion and IGA occur, whilst above 80% hydrogen embrittlement was found also. Sulphides were found to be deposited on the metal surface . 

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