The Chemistry of Fertilisers and Manure - Including Information on the Chemical Constituents and Types of Fertilisers and Manures

Frank Knowles

• Publisher: Barlow Press
• Year: 2011
• Print ISBN: 9781446531174
• eBook ISBN: 9781447490289
• Topic: Technology & Engineering
• Subtopic: Horticulture
• Index: Technology & Engineering

This early work on the fertilisers and manure concentrates on the chemistry behind them, examining their different types and how they are made. Written in simple, clear language and profusely illustrated, "The Chemistry of Fertilisers and Manure" will appeal to those with an interest in the history and development of modern agricultural techniques. Contents include: "Soil Science", "Fertilisers And Manures", "Nitrogenous Fertilisers", "Phosphatic Fertilisers", "Potassic Fertilisers", "Agricultural Salt", "Determination of Sodium Chloride", "Lime, Hydrated Lime And Carbonate Of Lime", "Mixed Or General Manures", "Potassium Nitrate", etc. Many vintage books such as this are increasingly scarce and expensive. It is with this in mind that we are republishing this volume now in an affordable, modern, high-quality edition complete with a specially-commissioned new introduction on soil science.

NITROGENOUS FERTILISERS

These contain nitrate, ammoniacal, cyanamide or organic nitrogen, but the percentage of nitrogen should always be stated as the element nitrogen.

Sulphate of Ammonia. There are two sources of supply, (1) the by-product from gas works and coke ovens, and (2) the synthetic product manufactured from the nitrogen of the atmosphere. The fertiliser usually contains about 21 per cent. of nitrogen, representing a purity of 99 per cent.

To show how Ammonia is obtained from Coal. When coal is heated in a closed vessel it is carbonised, gaseous products (coal gas) and liquid products (gas tar and gas liquor) are obtained and coke is left in the vessel. The gas liquor contains ammonia and ammonium salts.

Place some coal in a hard glass test tube and attach a delivery tube, bent at a right angle. Heat strongly and collect the tarry liquid which distils over. Pour off the upper aqueous layer into a test tube, add a little sodium hydroxide solution and heat. Note that ammonia is given off.

Determination of Free Acid. Weigh 20 gm. of the sample into a beaker, add about 100 ml. of distilled water and stir until dissolved. Add a few drops of methyl red as indicator, and titrate with o.1N. sodium hydroxide. Calculate the acidity as percentage by weight of sulphuric acid (H₂SO₄).

1 ml. of 0.1N. NaOH = 0.0049 gm. H₂SO₄.

The “neutral” grades of sulphate of ammonia should not contain more than 0.025 Per cent. of free acid expressed as sulphuric acid.

Determination of Nitrogen. Accurately weigh about 5 gm. of the sample and transfer to a 500 ml. graduated flask. Dissolve in water, make up to the mark and shake well. Pipette 25 ml. of the solution into the distilling flask of a nitrogen distillation apparatus. Add about 300 ml. of water, 10 ml. of 40 per cent. sodium hydroxide solution and a small amount of Devarda’s alloy. Distil into 50 ml. of 0.1N. sulphuric acid, and titrate the excess with 0.1N. sodium hydroxide. From the volume of acid neutralised by the ammonia, calculate the percentage of nitrogen in the sample.

1 ml. of 0.1N. H₂SO₄ = 0.0017 gm. NH₃ = 0.0014 gm. N.

Oxidation of Ammonia to Nitric Acid, Much of the nitric acid used in the manufacture of synthetic nitrogenous fertilisers is obtained by the oxidation of ammonia.

Place some platinised asbestos in a hard glass combustion tube. Attach a Woulffe’s bottle containing a strong solution of ammonia to one end and a tube leading into a distilling flask to the other end. Attach the side tube of the distilling flask to a suction pump and heat the platinised asbestos.

FIG. 8.—Apparatus for oxidation of ammonia.

Note that a liquid collects in the distilling flask, which also becomes filled with brown fumes. Test the liquid to show that it is nitric acid.

NH₃ + 2O₂ = HNO₃ + H₂O.

Nitrate of Soda. The natural product from Chili has been used for many years, but a synthetic product is now produced. The coarse crystalline form contains about 15.5 per cent. of nitrogen, representing a purity of 94 per cent., while a granulai form introduced in recent years contains at least 16 per cent. of nitrogen. Some sodium chloride is present, and the Chilian nitrate usually contains a trace of iodine combined as iodate.

Qualitative Test for Iodate. Dissolve a few gm. of the salt in water in a test tube, acidify with dilute hydrochloric acid, and add a few ml. of a weak solution of sodium sulphite. Test for free iodine by the addition of starch solution. If iodine is found, the presence of iodate is indicated, the iodate being reduced to iodine by the sulphur dioxide from the sodium sulphite.

2HIO₃ + 5SO₂ + 4H₂O = 5H₂SO₄ + I₂.

Determination of Chlorides. Weigh 5 gm. into a beaker, and add about 100 ml. of distilled water to dissolve the salt. Add a few drops of potassi...

Table of contents

• Cover
• Title
• Copyright
• Contents
• Fertilisers and Manures
• Nitrogenous Fertilisers
• Phosphatic Fertilisers
• Potassic Fertilisers
• Agricultural Salt
• Lime, Hydrated Lime and Carbonate of Lime