Tasting balance
A Trial Balance is a very sensitive balance with loose Einsetzschalen. Trial scales were in the fire assaying of the samplers for weighing ore - used and metal samples. Often three different test scales were used, the weighing scales, the river scales and the grain scales.
History
In 1550, Hanns Lamprecht from Nuremberg invented simple weighing scales. Around the year 1790, Hyacinth Magellan invented new weighing scales. The mechanic Magnie from Paris invented a particularly precise type of test balance. These scales were so accurate that they even hit 1/2000 of a grain .
construction
In order to achieve an exact result, the test scales must have a high degree of accuracy. Beam scales with the lowest possible tolerances were used as scales . The high accuracy was achieved because the axis of rotation of the balance beam was precisely aligned and the arms of the balance were of the same length. Due to the high accuracy of the scales, even dust particles in one of the weighing pans could have a negative effect on the result of very good scales. The scales were made of the best steel, which was easy to work with and was not easily attacked by rust. The steel was only hardened to the extent that it remained elastic and, after being deformed, jumped back into its original shape. Scales made from this steel could be built very finely and easily. In order to prevent dust from sticking to the suspensions of the weighing pans, the weighing pans of coin scales were hung on the balance beam with metal brackets. In the case of particularly sensitive scales, the suspensions for the weighing pans are made of horse hair or platinum wire.
Use of the three scales
The scales used had different sensitivities and load capacities. The weighing scales were designed for larger weights and were used to weigh the lead and the surcharges. The second scale was used to weigh the metals and ores to be sampled, it was more sensitive than the first. These first two scales were weighing scales. The grain scale was a weighing scale, it was the most sensitive of the scales used. It was used to weigh the gold or silver grains that remained in the sample form (chapel) during the abortion . This scale was very sensitive and could be seriously damaged by improper handling, as well as by incorrect use of this scale e.g. B. as a weighing scale. Grain scales are still used today to examine metal samples.
Setting up and handling the scales
The scales were attached to the wall with a bracket in such a way that the incident light fell on the side of the scales. In addition, a matt green screen was attached behind the scales. This served to protect the eyes. Sensitive sample scales could be influenced by drafts, uneven heating, dust and strong electrical or electromagnetic fields. To protect sensitive scales from dust, drafts and oxidation, they were kept in a glass case with doors. The case stood on three adjustable screws that allowed it to be aligned horizontally. A pendulum attached to the balance was used to check the exact alignment. In order to absorb moisture from the glass case, a glass filled with potash or calcium chloride was placed in the case. As protection against adverse effects from drafts - e.g. B. by opening the tasting room door - the workplace was protected by an additional wall of glass windows. The scales had to be protected from moisture, corrosive fumes and dust. Violent vibrations were also harmful to the scales. The tester had to make sure that the scales did not rust, as this would give inaccurate results.
The weighing
For weighing, sample items to be weighed were placed in one weighing pan and the sample weights in the other. When weighing in, the sample weights were placed on the left and when weighing on the right weighing pan. The sample could neither be hot nor significantly colder than the room temperature of the sample room. When the sample was hot, the scales were influenced by the air flow rising from the sample in such a way that the sample appeared lighter than it actually was. Sample material that was colder than the room temperature of the sample room absorbed the humidity and became heavier than before. In order to get an accurate result quickly when weighing, the sample weights were placed on the weighing pan in a fixed order. This brought the weight to be determined within ever narrower limits, so that it was ultimately accurate. The scales usually had to be locked in order to place or remove samples or weights. The sample was placed in matching bowls or boats made of thin sheet brass for weighing. If the sample could not be weighed directly in the bowl, it was filled into a glass tube with a stopper. After weighing, the sample was poured out again and the weight of the glass tube was determined. The difference between the two measurements was calculated and then gave the weight of the sample. Powdered substances were spread out on glossy paper, heaped up again and then weighed in portions so that a sample spoon filling of sample powder was placed on the weighing pan, this was then weighed and then another portion was added and weighed again. This was carried out until the weight was completely determined.
The trial weights
Various materials such as quartz or metals were used for the sample weights (measures of mass for determining the fineness of coins, ores and precious metal alloys). Agate or carnelian were used for quartz weights . The metallic sample weights consisted of the metals silver or platinum or of the alloys brass or argentan . Feather mark or aluminum was used for very small weights. Since brass oxidizes easily, it was initially unsuitable for the manufacture of precise weights. To compensate for this deficiency, brass weights were galvanically gold-plated before the first adjustment. Weights made of silver turned black with the formation of sulfur silver, but this had no noticeable influence on the measurement. The individual weights were checked on an accurate and sufficiently sensitive scale before the first use. There were gram weights and centners weights. The gram weights were divided into grams, decagrams, hectograms and kilograms. The centner weights were heavy depending on the country. There was the Upper Harz centnerweight, the Freiberg centnerweight, the Austrian centnerweight and a so-called older trial centnerweight. There was also the English trial weight, this was a gray weight based on the pharmacist's weight, Troy Weight.
Individual evidence
- ^ A b Carl Friedrich Richter: Latest mountain and hut lexicon. First volume, Kleefeldsche Buchhandlung, Leipzig 1805
- ^ Johann Christoph Stößel (Ed.): Mining dictionary. Chemnitz 1778.
- ^ Gabriel Christoph Benjamin Busch : Handbook of Inventions. Tenth part, second division, by Johann Friedrich Berecke, Eisenach 1820.
- ↑ a b c d e Bruno Kerl: TH. Bodemann's instructions for the art of mining and smelting. second edition, Verlag der Grosseschen Buchhandlung, Clausthal 1856.
- ^ CE Gellert: Johann Andrea Cramer's beginnings of the art of tasting. Publishing house of the Heinsiussische Buchhandlung, Leipzig 1766.
- ↑ a b c d e f g h Bruno Kerl: Metallurgical trial art for use in lectures and for self-study. Published by Arthur Felix, Leipzig 1866
- ^ Georg Agricola: Twelve books on mining and metallurgy. In commission VDI-Verlag GmbH, Berlin.
- ^ Theodor Bodemann: Instructions for the art of mining and smelting. Verlag der Schweizerische Buchhandlung, Clausthal 1845.
- ↑ Helmut Kahnt, Bernd Knorr: Old dimensions, coins and weights. A lexicon. Bibliographisches Institut, Leipzig 1986, licensed edition Mannheim / Vienna / Zurich 1987, ISBN 3-411-02148-9 , p. 394 f.