Ferrous sulphate solution

Fenton s reagent. To a solution of tartaric acid or a tartrate add 1 drop of freshly prepared ferrous sulphate solution, i drop of hydrogen peroxide solution and then excess of NaOH solution an intense violet coloration is produced, due to the ferric salt of dihydroxyfumaric acid, HOOC C(OH) C(OH)COOH. 

CAUTION. Ethers that have been stored for long periods, particularly in partly-filled bottles, frequently contain small quantities of highly explosive peroxides. The presence of peroxides may be detected either by the per-chromic acid test of qualitative inorganic analysis (addition of an acidified solution of potassium dichromate) or by the liberation of iodine from acidified potassium iodide solution (compare Section 11,47,7). The peroxides are nonvolatile and may accumulate in the flask during the distillation of the ether the residue is explosive and may detonate, when distilled, with sufficient violence to shatter the apparatus and cause serious personal injury. If peroxides are found, they must first be removed by treatment with acidified ferrous sulphate solution (Section 11,47,7) or with sodium sulphite solution or with stannous chloride solution (Section VI, 12). The common extraction solvents diethyl ether and di-tso-propyl ether are particularly prone to the formation of peroxides. 

Critical relative humidity The primary value of the critical relative humidity denotes that humidity below which no corrosion of the metal in question takes place. However, it is important to know whether this refers to a clean metal surface or one covered with corrosion products. In the latter case a secondary critical humidity is usually found at which the rate of corrosion increases markedly. This is attributed to the hygroscopic nature of the corrosion product (see later). In the case of iron and steel it appears that there may even be a tertiary critical humidity . Thus at about 60% r.h. rusting commences at a very slow rate (primary value) at 75-80% r.h. there is a sharp increase in corrosion rate probably attributable to capillary condensation of moisture within the rust . At 90% r.h. there is a further increase in rusting rate corresponding to the vapour pressure of saturated ferrous sulphate solution , ferrous sulphate being identifiable in rust as crystalline agglomerates. The primary critical r.h. for uncorroded metal surfaces seems to be virtually the same for all metals, but the secondary values vary quite widely. 

In a standard method [15, 19] soil organic matter is almost completely oxidized by boiling gently with a solution of potassium dichromate, sulphuric acid and phosphoric acid. Excess dichromate is determined by titration with standard ferrous sulphate solution. 

Tabun may be detected by the air-flow method, by aspirating into ferrous sulphate solution to which a few drops of 10 per cent sodium hydroxide has been added. The mixture is then boiled and acidified with dilute sulphuric acid and filtered to observe the blue specks of Prussian blue on the filter paper. 

Procedure Triturate 3.5 g thoroughly with 35 ml DW, fdter and decolorise the filtrate by the addition of a little zinc powder. To 5.0 ml of the filtrate add a few drops of ferrous sulphate solution and 1 ml NaOH solution warm gently and acidify with HC1, no blue colour or green colour is produced. 

This ferrous sulphate solution is standard toed against semi-normal potassium permanganate solution on t.ho same day, using the same pipette. 

Nitrates. — Dissolve 1 gm. of mercuric oxide in 2 cc. of water and 2 cc. of sulphuric acid, and overlay this mixture with 1 cc. of ferrous sulphate solution. No colored zone should form even on long standing. 

Nitrates. — On mixing 2 cc. of the 1 10 solution with 2 cc. of concentrated sulphuric acid, and overlaying this mixture with 2 cc. of ferrous sulphate solution, no brownish-red zone should develop at the contact-surfaces of the two liquids, even on long standing. 

Nitrates. — Dissolve 0.2 gm. of potassium rarbinmle in 2cc. of dilute sulphuric acid, and mix the fluid with 2 < . of concentrated suphuric acid. On now cooling. solution, and overlaying it with 1 re. of a ferrous sulphate solution, no reddish-brown zone should form at tin- contact surlnees of the two liquids. 

Electrometric Methods have been applied for the estimation of vanadium alone and alloyed with other metals, e.g. iron, chromium, uranium. The reduced solution is either gradually oxidised by means of a suitable oxidising agent (potassium permanganate, ammonium persulphate, nitric acid), or the vanadate solution is gradually reduced with ferrous sulphate solution the changes in the E.M.F. of a suitable cell indicate the end point.8... 

When heated, the salt first melts and at a higher temperature it decomposes to form silver 7 reduction to the metal occurs more readily when heated with carbon.8 Partial reduction also occurs when the orthoarsenate is treated with formaldehyde 9 or with ferrous sulphate solution 10 in the former ease silver is formed, but in the latter silver suboxide. 

The liquid is made alkaline with potassium hydroxide and heated to boiling with a few drops of ferrous sulphate solution. A little ferric chloride is next added to the liquid, which is cooled and acidified with hydrochloric acid in presence of hydrocyanic acid a blue precipitate is obtained or a greenish-blue liquid which deposits blue flocks on standing. 

Procedure, ioo c.c. of the wine are evaporated in a flask to io c.c., allowed to cool and treated with 6 c.c. of the saturated ferrous sulphate solution and 4 c.c. of concentrated sulphuric acid.1 The flask is connected with a vertical condenser about 50 cm. long and heated carefully over a small flame so that excessive frothing of the mass is avoided. The distillate is collected in two or three well-cleaned tubes, each containing 2-3 c.c. of the iodide-starch paste acidified with 2 drops of dilute sulphuric acid the tubes are inclined so that the distillate flows down the walls. In presence of nitrites, a blue ring forms at the zone of separation between the starch and the distillate. 

To one portion of the ferrous sulphate solution add 45 grams of ammonium sulphate and 5 cc. of 6 N H2SO4. From the solubility data given below determine the volume of solution required to crystallize ferrous ammonium sulphate. (Note that the data are for anhydrous salts.) After your instructor has checked your result, adjust the volume to the proper value. Filter the solution if it is not clear, and allow it to stand in a crystallizing dish until a satisfactory yield of the double salt has formed. Decant the mother liquor from the crystals, and wash them with a little distilled water. Dry them thoroughly at room temperature with white paper towels. 

Pressure exerts an important influence upon the rate of oxidation. Thus silicon, ethane, phosphorus, arsenic, and several other substances, are found to oxidise more readily at low oxygen pressures on the other hand, the rates of the rusting of iron and the oxidation of ferrous sulphate solution are accelerated by increase of pressure. 

Acid dichromate and alkaline permanganate may also be used as oxidising agents, the excess being determined iodometrically and with ferrous sulphate solution respectively. 

Ferrous iodate.—On addition of potassium iodate to ferrous sulphate solution, a pale yellow precipitate is obtained, consisting probably of ferrous iodate.4... 

It is stable in contact with ferrous sulphate solution at temperatures above 64-4° C., which point is the transition temperature in these circumstances between the mono- and tetra-hydrates.5 Its heat of solution6 in water at 13 5° C. is 7538 calories. It absorbs ammonia vapour, yielding the pentammoniate, FeS04.5NHa.H20.7... 

The rate of oxidation of ferrous sulphate solution upon exposure to air is proportional to the partial pressure of the oxygen.2 Hence it is reduced by addition of concentrated solutions of inert soluble salts, such as chlorides and sulphates of sodium, potassium, and magnesium, owing to their presence causing a decrease in the solubility of the oxygen.3 The oxidation depends upon the un-ionised portion of the dissolved salt. 

Ferric ammonium alum or Iron ammonium alum, (NH4)2S04. Fe2(S04)3.24H20, has been obtained by electrolysing a solution of ferrous sulphate and ammonium sulphate.3 The cathode consists of platinum wire immersed m acidified ferrous sulphate solution contained in a porous pot. An acidulated solution of ferrous and ammonium sulphates surrounds the pot, and is contained m a platinum dish which serves as anode. A current of 0-04 ampere is passed through the cell, and after several hours crystals of the alum are deposited round the anode. 

The salt may also be obtained by triturating a concentrated solution of ferrous sulphate with barium thiosulphate,1 but it is less pure, as it contains some tetrathionate as well.2 It results when sulphur is digested with ferrous sulphate solution, and when iron is dissolved in aqueous sulphurous acid.3 This latter reaction is somewhat complicated, ferrous sulphite being first produced, thus —... 

Iron Selenites.—Although metallic iron does not appear to be soluble in selenous acid, yet selenites of iron are readily obtained in a variety of ways. When sodium selenite is added to ferrous sulphate solution, a white precipitate of ferrous selenite, FeSe03, is obtained.4 This becomes darker on exposure to air in consequence of oxidation. If the white precipitate is dissolved in hydrochloric acid, a portion of the selenium separates out, whilst ferric chloride and selenous acid remain in solution. Thus —... 

K20.3Fe203.4Cr03—a yellowish brown micro-crystalline precipitate, obtained by addition of excess of potassium chromate to ferrous sulphate solution. 

It may be prepared by the action of disodium hydrogen arsenate upon ferrous sulphate solution —6... 

Ferrous thiocarbonate, FeCS3.—On adding an alkali thiocarbonate to ferrous sulphate solution a red liquid is obtained, which gradually becomes darker in colour on standing. The solution is believed to contain ferrous thiocarbonate (Berzelius). 

The crude coal gas is washed with ferrous sulphate solution, whereby the latter is converted into a suspension of ferrous sulphide in ammonium sulphate solution. This reacts with the ammonium cyanide, yielding ferrous ferrocyanide, Fe2[Fe(CN)6], or ammonium ferrous ferrocyanide, (NH4)2Fe[Fe(CN)6], according to circumstances. Potassium ferrocyanide may be obtained from these by treatment with lime, as m the spent oxide process. By repeatedly dissolving in water and precipitating with alcohol, the salt can be obtained in a very pure state.1... 

Colour Tests. To 0.2 ml add 2 ml of a 2% ferrous sulphate solution and 5 ml of dilute hydrochloric acid—green-brown to 0.2 ml add 0.5 ml of aniline and 5 ml of acetic acid—orange-red. 

Copper, Nitric Acid, etc. (Alkali Salts, Calcium). — Dilute 20 iM. of ferric chloride solution (1 1) with 100 cc. of water, fuld 25 cc. of ammonia water, and filter. On evaporating 50 cc. of the colorless filtrate and igniting the residue, the weight of the latter should not exceed 0.001 gm. On mixing 2 cc. of the filtrate with 2 cc. of concentrated sulphuric acid, and overlaying tliis mixture with 1 cc. of ferrous sulphate solution, no brown zone should form at the contact-surfaces of the two licpiids. 20 cc. of the filtrate acidulated With acetic a

potassium ferrocyanide solution. 

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