I read recently that in northern Europe in the early 1900s human urine was collected for use in the manufacture of matches. Are there any other known uses for urine?

Urine has been collected for many different purposes throughout history, for its ammonia content and because of its ability to form saltpetre.

From the late Middle Ages through to the early 20th century, people collected urine, filtered it through rotting straw and then left it to stand for about 12 months. After that, the chemical salts that had formed were washed from the straw with water, and this slurry was left to evaporate in the sun, eventually leaving saltpetre (potassium nitrate). This was often used in slow-burning matches, but its primary use was in gunpowder, where it was added to sulphur and charcoal to make black powder, the variant of gunpowder used in firearms.

The second major use for urine in history has been as a mordant: a substance used to prepare textiles for dyeing. The ammonia in the urine was extracted by similar means to saltpetre, and used mainly to create green and indigo. This process was prominent in the Nottingham area, perhaps explaining why Robin Hood and his merry men were depicted wearing green.

Fortunately, in modern times both potassium nitrate and ammonia can be obtained through the Haber process, whereby nitrogen and hydrogen are reacted over an iron substrate.

Ashley Jones, Stratford-upon-Avon

The use of urine in chemical compounds dates back to 1669, when the German alchemist Hennig Brand (also known as Doctor Teutonicus) tried to extract gold from human urine, using about 60 bucketfuls per experiment. He succeeded in obtaining a white, waxy substance that glowed in the dark. This was phosphorus, which, today, is extracted from phosphate minerals.

Ron Murray, Kilmarnock, Ayrshire

Urine contains mineral nutrients that are essential for plant growth. The idea of using it as a fertiliser is not new. The Latin author Columella wrote, around AD50: “Human urine, if you let it age for six months and then apply it to vines or fruit trees, there is nothing that makes them bear more abundantly; and not only will this treatment produce a larger crop but also it improves the flavour and the bouquet of the wine and the fruit.”

Edward Newman, Bristol

What is the word for the sound of the sea gently lapping on a gravel shore? I like the word susurration, for the sound of the wind through trees, but cannot find one for this.

The Oxford American Dictionaries offer a definition of “susuration”which includes the phrase “the susurrus of the stream”. Thus, the word not only refers to the sound of wind through trees but also the flow and lapping of water.

Robert Randell, London SE26

The word, surely, is simply “sibilance”, as in D.H. Lawrence's poem, Spray: “A wave bursts in anger on a rock, broken up/ In wild white sibilant spray.”

Mark Jarvis, London E8

Whenever I stand on a shingle beach listening to waves gently lapping the stones, I recall Aeschylus's phrase: “the unending laughter of the waves”. The word, then, must be “laughing”. Perhaps we might talk of wavelets “tittering along the shore?”

Patrick Martin, Winchester, Hants

The Greeks, of course, had an exact word for it — phloisbos. It first appears in Homer, and describes the murmur of the sea on a gravel shore. It survives to this day in Greece in the name of shoreline cafés and hotels.

Martin Hodgson, Sheffield

Why do we in Britain refer to the River Tees, River Cam, etc and not to the Tees River, Cam River etc?

May I, as a native-born Cumbrian, take up the answer of Tom Bloomfield (Q&A, Dec 7), who states: “There is only one lake in the English Lake District; all the others are meres, waters or tarns. Bassenthwaite Lake is unusual in being named after its village.” The correct name for the lake at Bassenthwaite is Bass Lake, which, I have always understood, was named after the species of fish within it. “Thwaite” is Old Norse for water, usually meaning “community by the water”. Therefore the village of Bassenthwaite is named after the lake, not the reverse.

T.L.Hewitt, Ulverston, Cumbria

How are “seedless” fruits, such as grapes, satsumas etc produced? With no seeds, how do they ensure future supplies?

Paul Motte-Harrison, Shoreham-by-Sea, W Sussex

Do we know, or is there a story to explain, what happened to the presents of gold, frankincense and myrrh given to Jesus?

Chris Tinkler, Kirkbymoorside, N Yorks

Do any cultures have a question, or questions, that must never be asked?

Edith Edge-Spiro, Manchester

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