“Carbon black, also called charcoal black lamp black, pigment black, soot or black carbon, is a fine particle carbon pigment obtained as soot from the incomplete combustion of many different types of organic materials, such as natural gas, or oil. Carbon black is usually a fine, soft, black powder. It is very stable and unaffected by light, acids and alkalis. It is commonly used in printing and lithograph inks and in Chinese ink sticks. In industry, carbon black is used as a filtration material and a filler /pigment in coatings, rubber, plastics, paints, carbon paper, and crayons. Continue reading
As described in Section 6 of ASTM D1209, there are 2 criteria to validate a APHA/Pt-Co 500 standard: Continue reading
Per Section 6.2 of ASTM D1209 Standard Test Method for Color of Clear Liquids (Platinum Cobalt Scale):
“When properly sealed and stored the standards are stable for at least a year and do not degrade markedly for 2 years.”
Our industrial experience is that if kept properly stoppered in amber bottles, the APHA/Pt-Co/Hazen visual color standards do not degrade significantly for longer than 2 years but this is the time frame that most sources reference as optimal.
If you have a dated APHA/Pt-Co/Hazen 500 liquid color standard, one validation method would be to see if it still meets the absorbance tolerance limits of ASTM D1209 Table 1, and is effectively clear (ASTM D1003 Haze% < 2).
A literature reference on stability of the APHA/Pt-Co/Hazen color standards can be found at:
Scharf, W. W., Ferber, K. H., and White, R. G., “Stability of Platinum-Cobalt Color Standards,” Materials Research and Standards, Vol. 6, No 6, June 1966 pp 302-304.