Joseph Proust

Madrid, 1787

Proust was inaccurately thought to be the discoverer of silver in seawater. Actually he had observed tarnished silver in San Pedro de Alcantara's shipwreck off the coast of Portugal, which was later misinterpreted in 1859. 

San Pedro de Alcantara was a 64-gun Spanish man-of-war, built in Cuba in 1770, which sank near Peniche, Portugal, loaded with so much treasure that her shipwreck shocked the financial markets of Spain in 1786. The cargo was about twice as much as usual for such a ship. She sailed from Peru in 1784 with a load of 600 tons of copper, 153 tons of silver and four tons of gold from Peruvian mines. In a dark February night of 1786, she hit a rock near Peniche, 90 km north of Lisbon. 

Shipwreck of the ship of War San Pedro de Alcantara near Peniche

Shipwreck of the ship of War San Pedro de Alcantara near Peniche, Image: Vicente Mariani


The silver was mined in the tiny Bolivian village of Potosi that was once the largest industrial mining complex in the world

Proust suggested the acidic seawater tarnished the silver. This was alarming because the silver was minted to coins in Lima, mostly 8 reales pieces, "pieces of eight"Although the mint said the silver could be fully recovered, there was a fear of loss of considerable amount of silver due to corrosion. King Charles III of Spain then ordered these silver should never leave the country in fear of fall of economy. Proust also mentioned gold was unaffected in seawater. 


The pieces of eight were minted at Casa de Moneda de Lima

               

Silver and Gold Eight Royals Coin of Charles III of Spain

The copper, silver, and gold lost in San Pedro’s cargo corresponded to about 1/12 of the total currency circulating in Spain. The Spanish king was alarmed and immediately sent his representative to the site. An enormous diving enterprise was initiated and divers were hired from all around. During the following three years more than 40 divers worked full-time, and almost all of the cargo was salvaged. This was considered a great success, since the cargo was worth much more than the ship. The diving operation was by then the largest ever in European history.

Joseph Louis Proust 

Joseph Louis Proust (26 September 1754 – 5 July 1826) was a French chemist. He was best known for his discovery of the law of constant composition in 1794, stating that chemical compounds always combine in constant proportions. In 1787 he was in service of the Spanish king and was teaching chemistry in Madrid. 

De L’action Des Eaux De La Mer Sur L’argent

posted Jun 10, 2017, 7:42 AM by John Doe

De L’action Des Eaux De La Mer Sur L’argent

Si le lit fur lequel repofent les eaux de l’océan deviant un jour terre habitable, fi la preffion de l’air doit fuccéder à celle des mers, comme tous les phénoménes géologiques femblent le promettre, les homes qui fouleront alors ce continent nouveau parviendront fans dourte à rettouver ces immenfes tréfors que la voracité des mers ne ceffe d’engloutir depuis que le nouveau monde eft fréquenté de l’ancien. L’événement du naufarge que le vaiffeau le Saint-Pierre-d’Alcantara a fait fur les côtes de Portugal vient de nous mettre à portée de prédire la méramorphofe fous laquelle l’argent fe montrera dans les tems à venir. L’acide marin, ce premier element de la falure des mers, dérogent à l’attraĉtion qui le fixe à fa bafe aura changé ce metal en mine d’argent cornée. Le court efpace de tems écoulé depuis le moment du naufrage à celui où on a pu rerirer les efpéces monnoyées a fuffi pour en attaquer la furface à un quart de ligne de profondeur. Ces pieces font forties de la mer recouvertes d’une couche noire qui s’en fépare en écailles que j’ai reconnues pour de l’argent corné. La bienveillance du Monarque n’a point voulu que cette perte de poid tombât fur fes fujets, en conféquence il a éré ordonné que ces efpéces ne fortiroient point du royaume : comme ces écailles d’argent corné ont dŭ tomber au premier frottement des pieces, il fera aifé d’en prévenir la perte dans des circonftances pareilles. Les Hôtels des monnoies avertis que l’argent corné peut étte rétabli fans perte, réclameroient fans doute ces debris pour les reftituer à l’état d’argent pur par les procédés que la plupart des ouvrages de éhimie indiquent. L’or n’avoit fouffert aucune alteration.

Je fuis, &c.

Madrid, ce 4 avril 1787.  


Source: 
Journal de physique, de chimie, d'histoire naturelle et des arts 30, 396 (1787).

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