DOI: https://doi.org/10.15587/1729-4061.2019.165408

Improving a procedure for determining the assay of gold in a precious alloy of different composition using a touchstone

Tatyana Artyukh, Galyna Kupalova, Viktor Bazylevych, Inna Hryhorenko, Alla Ternova

Abstract


We report testing the yellow and white jewelry alloys based on gold that contains nickel, zinc, palladium, using a touchstone by applying various chemical reagents and XFA (X-ray fluorescence analysis).

We have improved the procedure for assessing the conformity of assay of the precious alloys based on gold, considering the content of component composition by using the results from rubbing the alloys on a touchstone.

It was established that the magnitude of gold assay for precious alloys in the system AuAgZnCu, determined under the action of the reagent "chloric gold" on the touchstone, depends on the manifestation of contrast in the course of quality reaction against a standard sample (touch-needle).

Under the influence of the reagent, the "yellow" gold alloys demonstrate chloride compounds with silver and copper, being reduced to a metal powder of black and brown color. In this case, copper dissolves while gold, together with silver, forms an intensive residue on a strip that depends on the ligature composition of the alloy. It was established that the lower the assay of a tested sample, the greater the amount of "chlorine gold" that decomposes, the larger the sediment of silver chloride and the pure gold reduced from the reagent, and hence the darker the sediment.

It has been proven that testing the precious alloys of red color from the system AuAgZnCu 585 with a content of zinc (over 2 %), nickel, indium by using a reagent based on potassium dichromate and copper chloride is not effective.

The results of our analysis indicate the increased gold assay compared with a standard touch-needle.

To eliminate this phenomenon, it is recommended that one should first determine the composition of an alloy by the XFA method and construct an algorithm for testing in accordance with the content of the alloy by other reagents.

It was determined that the gold assay defined on a touchstone for alloys from the system AuAgZnCu 585 (a content of zinc is over 2 %) is more contrast under the influence of acidic reagents and depends on the component composition of the alloy.

It has been proven that the alloy of "white gold", composed of palladium and silver (AuAgPd585), is not affected by the acid reagent for gold assay 585.

Testing the alloy of "white gold" (AuAgPd585) using an acid reagent for gold assay 750 yields the dark sediment of a bluish tint.

We have established a more contrast effect on the alloys of "white gold" and "yellow gold" of assay 750 from the acid reagent for gold alloys of assay 750.


Keywords


gold alloys; touchstone; "chlorine gold"; potassium dichromate; copper sulphate; assay control

References


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Pro derzhavne rehuliuvannia vydobutku, vyrobnytstva i zastosuvannia dorohotsinnykh metaliv i dorohotsinnoho kaminnia ta kontrol za operatsiyamy z nymy: Zakon Ukrainy vid 08.11.1997 No. 637/97-ВР. Available at: https://zakon.rada.gov.ua/laws/show/995-16

DSTU 3527-97. Vyroby zolotarski z koshtovnykh metaliv. Zahalni tekhnichni umovy (1997). Kyiv, 31.

Pro Pravyla torhivli dorohotsinnymy metalamy (krim bankivskykh metaliv) i dorohotsinnym kaminniam, dorohotsinnym kaminniam orhanohennoho utvorennia ta napivdorohotsinnym kaminniam u syromu ta obroblenomu vyhliadi i vyrobamy z nykh, shcho nalezhat subiektam hospodariuvannia na pravi vlasnosti: Postanova Kabinetu Ministriv Ukrainy vid 04.06.1998 No. 802. Available at: https://zakon.rada.gov.ua/laws/show/802-98-%D0%BF

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Artyukh, T., Hryhorenko, I., Ternova, A., Yaheliuk, S., Cernavca, M. (2018). Influence of the alloy composition on determining the millesimal fineness of gold by X-ray fluorescent and assay analysis. Eastern-European Journal of Enterprise Technologies, 5 (12 (95)), 6–18. doi: https://doi.org/10.15587/1729-4061.2018.142730

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Pro zatverdzhennia Instruktsiyi pro zdiysnennia derzhavnoho ekspertno-probirnoho kontroliu za yakistiu yuvelirnykh ta pobutovykh vyrobiv z dorohotsinnykh metaliv: Nakaz Ministerstva finansiv Ukrainy vid 20.10.1999 No. 244. Available at: https://zakon.rada.gov.ua/laws/show/z0874-99

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Finkelstein, N. P. (1962). A critical review of methods for the assay and analysis of high purity gold bullion. Journal of the Southern African Institute of Mining and Metallurgy, 62 (12), 700–711.

Oddy, W. A. (1986). The touchstone: the oldest colorimetric method of analysis. Endeavour, 10 (4), 164–166. doi: https://doi.org/10.1016/0160-9327(86)90089-x

Ježek, M. (2013). Touchstones of archaeology. Journal of Anthropological Archaeology, 32 (4), 713–731. doi: https://doi.org/10.1016/j.jaa.2013.04.004

Marucco, A. (2004). Low-energy ED-XRF spectrometry application in gold assaying. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 213, 486–490. doi: https://doi.org/10.1016/s0168-583x(03)01608-2

Stankiewicz, W., Bolibrzuch, B., Marczak, M. (1998). Gold and gold alloy reference materials for XRF analysis. Gold Bulletin, 31 (4), 119–125. doi: https://doi.org/10.1007/bf03214776

Young, R. S. (1980). Analysis for gold. Gold Bulletin, 13 (1), 9–14. doi: https://doi.org/10.1007/bf03215123

Jurado-López, A., de Castro, L., Pérez-Morales, R. (2006). Application of energy-dispersive X-ray fluorescence to jewellery samples determining gold and silver. Gold Bulletin, 39 (1), 16–21. doi: https://doi.org/10.1007/bf03215528

Mahr, C., Schowalter, M., Mitterbauer, C., Lackmann, A., Fitzek, L., Mehrtens, T. et. al. (2018). Nanoporous gold dealloyed from AuAg and AuCu: Comparison of structure and chemical composition. Materialia, 2, 131–137. doi: https://doi.org/10.1016/j.mtla.2018.07.014

Morcali, M. H., Zeytuncu, B., Ozlem, E., Aktas, S. (2015). Studies of Gold Adsorption from Chloride Media. Materials Research, 18 (3), 660–667. doi: https://doi.org/10.1590/1516-1439.005715

Henson, B. C., Harris, J. T., Homan, K. A. (2017). Synthesis of Gold Nanorods: Avoiding Common Pitfalls. Material Matters. Available at: https://www.sigmaaldrich.com/technical-documents/articles/material-matters/synthesis-of-gold-nanorods.html

Ali, R., Ali, H. R. H., Batakoushy, H. A., Derayea, S. M., Elsutohy, M. M. (2019). A reductant colorimetric method for the rapid detection of certain cephalosporins via the production of gold and silver nanoparticles. Microchemical Journal, 146, 864–871. doi: https://doi.org/10.1016/j.microc.2019.02.023

Hashmi, M. H., Rashid, A. (1966). Colorimetric Determination of Gold, Platinum, and Cerium. Analytical Chemistry, 38 (10), 1423–1424. doi: https://doi.org/10.1021/ac60242a041

TU U 27.4-00201514-010:2005. Splavy na osnovi dorohotsinnykh metaliv. Tekhnichni umovy (2005). Donetsk, 12.


GOST Style Citations


Pro zakhyst prav spozhyvachiv: Zakon Ukrainy vid 12.05.1991 No. 1024-XII. URL: https://zakon.rada.gov.ua/laws/show/1023-12/print

Pro derzhavne rehuliuvannia vydobutku, vyrobnytstva i zastosuvannia dorohotsinnykh metaliv i dorohotsinnoho kaminnia ta kontrol za operatsiyamy z nymy: Zakon Ukrainy vid 08.11.1997 No. 637/97-ВР. URL: https://zakon.rada.gov.ua/laws/show/995-16

DSTU 3527-97. Vyroby zolotarski z koshtovnykh metaliv. Zahalni tekhnichni umovy. Kyiv, 1997. 31 p.

Pro Pravyla torhivli dorohotsinnymy metalamy (krim bankivskykh metaliv) i dorohotsinnym kaminniam, dorohotsinnym kaminniam orhanohennoho utvorennia ta napivdorohotsinnym kaminniam u syromu ta obroblenomu vyhliadi i vyrobamy z nykh, shcho nalezhat subiektam hospodariuvannia na pravi vlasnosti: Postanova Kabinetu Ministriv Ukrainy vid 04.06.1998 No. 802. URL: https://zakon.rada.gov.ua/laws/show/802-98-%D0%BF

Document 31994L0027 // Eur-Lex. URL: https://eur-lex.europa.eu/legal-content/LV/NIM/?uri=CELEX:31994L0027

Influence of the alloy composition on determining the millesimal fineness of gold by X-ray fluorescent and assay analysis / Artyukh T., Hryhorenko I., Ternova A., Yaheliuk S., Cernavca M. // Eastern-European Journal of Enterprise Technologies. 2018. Vol. 5, Issue 12 (95). P. 6–18. doi: https://doi.org/10.15587/1729-4061.2018.142730 

Nazymok M. M., Borovykov O. Ya., Artiukh T. M. Probirnyi kontrol. Metody analizu dorohotsinnykh metaliv. Kyiv, 2010. 368 p.

Pro zatverdzhennia Instruktsiyi pro zdiysnennia derzhavnoho ekspertno-probirnoho kontroliu za yakistiu yuvelirnykh ta pobutovykh vyrobiv z dorohotsinnykh metaliv: Nakaz Ministerstva finansiv Ukrainy vid 20.10.1999 No. 244. URL: https://zakon.rada.gov.ua/laws/show/z0874-99

HSTU 47-083-02.8-2018. Splavy dorohotsinnykh metaliv yuvelirni. Metody vyprobuvannia na probirnomu kameni yuvelirnykh ta pobutovykh vyrobiv z dorohotsinnykh metaliv, vyrobiv ta materialiv, shcho mistiat dorohotsinni metaly. Kyiv, 2018. 27 p.

Blagorodnye metally / Bredihin V. N., Kozhanov V. A., Manyak N. A., Kushnerova Е. Yu. Doneck: GVUZ «DonNTU», 2009. 525 p.

Finkelstein N. P. A critical review of methods for the assay and analysis of high purity gold bullion // Journal of the Southern African Institute of Mining and Metallurgy. 1962. Vol. 62, Issue 12. Р. 700–711.

Oddy W. A. The touchstone: the oldest colorimetric method of analysis // Endeavour. 1986. Vol. 10, Issue 4. P. 164–166. doi: https://doi.org/10.1016/0160-9327(86)90089-x 

Ježek M. Touchstones of archaeology // Journal of Anthropological Archaeology. 2013. Vol. 32, Issue 4. P. 713–731. doi: https://doi.org/10.1016/j.jaa.2013.04.004 

Marucco A. Low-energy ED-XRF spectrometry application in gold assaying // Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 2004. Vol. 213. P. 486–490. doi: https://doi.org/10.1016/s0168-583x(03)01608-2 

Stankiewicz W., Bolibrzuch B., Marczak M. Gold and gold alloy reference materials for XRF analysis // Gold Bulletin. 1998. Vol. 31, Issue 4. P. 119–125. doi: https://doi.org/10.1007/bf03214776 

Young R. S. Analysis for gold // Gold Bulletin. 1980. Vol. 13, Issue 1. P. 9–14. doi: https://doi.org/10.1007/bf03215123 

Jurado-López A., de Castro L., Pérez-Morales R. Application of energy-dispersive X-ray fluorescence to jewellery samples determining gold and silver // Gold Bulletin. 2006. Vol. 39, Issue 1. P. 16–21. doi: https://doi.org/10.1007/bf03215528 

Nanoporous gold dealloyed from AuAg and AuCu: Comparison of structure and chemical composition / Mahr C., Schowalter M., Mitterbauer C., Lackmann A., Fitzek L., Mehrtens T. et. al. // Materialia. 2018. Vol. 2. P. 131–137. doi: https://doi.org/10.1016/j.mtla.2018.07.014 

Studies of Gold Adsorption from Chloride Media / Morcali M. H., Zeytuncu B., Ozlem E., Aktas S. // Materials Research. 2015. Vol. 18, Issue 3. P. 660–667. doi: https://doi.org/10.1590/1516-1439.005715 

Henson B. C., Harris J. T., Homan K. A. Synthesis of Gold Nanorods: Avoiding Common Pitfalls // Material Matters. 2017. URL: https://www.sigmaaldrich.com/technical-documents/articles/material-matters/synthesis-of-gold-nanorods.html

A reductant colorimetric method for the rapid detection of certain cephalosporins via the production of gold and silver nanoparticles / Ali R., Ali H. R. H., Batakoushy H. A., Derayea S. M., Elsutohy M. M. // Microchemical Journal. 2019. Vol. 146. P. 864–871. doi: https://doi.org/10.1016/j.microc.2019.02.023 

Hashmi M. H., Rashid A. Colorimetric Determination of Gold, Platinum, and Cerium // Analytical Chemistry. 1966. Vol. 38, Issue 10. P. 1423–1424. doi: https://doi.org/10.1021/ac60242a041 

TU U 27.4-00201514-010:2005. Splavy na osnovi dorohotsinnykh metaliv. Tekhnichni umovy. Donetsk, 2005. 12 p.







Copyright (c) 2019 Tatyana Artyukh, Galyna Kupalova, Viktor Bazylevych, Inna Hryhorenko, Alla Ternova

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ISSN (print) 1729-3774, ISSN (on-line) 1729-4061