Sulfide staining

Foods such as meat, fish, and some vegetables contain sulfur-bearing amino acids that form volatile sulfur compounds during processing and storage. When these compounds react with iron, a black precipitate forms on the container and in most instances darkens the food. A small piece of aluminum welded to the tinplate can has been used to prevent container corrosion and sulfide staining in commercially canned hams. In this case, the aluminum acts as a sacrificial anode and stops the reaction with tin and iron that otherwise could occur at the small exposed tinplate areas (14). 

This ammonium sulfide staining procedure of the uterus to detect early implantation scars is not applicable to rabbits (11). 

Seiler, B.C. 1968. The mechanism of sulfide staining of tin foodpacks. Food Technol. 22 1425-1429. 

Lead Compounds—These were among the earliest stabilizers. Although quite effective as heat stabilizers, they are toxic, impart opacity to PVC compounds, and cause black coloration with time because of poor sulfide stain resistance. The primary use for lead compounds is in electric applications such as wire coatings. The principal lead compounds for this use are tribasic lead sulfate, basic lead sulfate silicate, basic lead carbonate, and basic lead phthalate. Use levels usually range from 3 to 8 parts-per-hundred parts of PVC (phr). 

Metal Soaps—Barium and cadmium stabilizers are less toxic than lead and have lower cost on the basis of use levels, better sulfide stain resistance, and good clarity. They are a major class of heat stabilizers. Calcium and zinc soaps are also included in this classification because of their similar performance. The soaps used are based on a wide variety of anions such as octoates (2-ethyIhexanoic acid derived), benzoates, laurates, stearates, and substituted phenolates. 

Organotin Compounds—These offer good overall stabilization with excellent clarity and complete freedom from sulfide staining. They are more expensive than the common barium-cadmium types as a result of the higher tin metal prices. The commercially important tin stabilizers include various dibutyltin and dimethyltin salts of maleate half esters, alkyl mercaptans, and thioacids, as well as certain monoalkyltin derivatives. Certain... 

ASTM D1712-96, "Standard Test Method for Resistance of Plastics to Sulfide Staining," Philadelphia (1996). 

ASTM D1712. Resi.stance of plastics to sulfide staining. 1989. 

Non-sulfide staining fiim. [Data from Pautai industrial Coipomtion,T3iwm.]... 

The relaxation process significantly alters the stress/strain properties of the fiber and can be incorporated in the drying as a continuous stage, or can be carried out by a batch process where the fiber is subjected to a hot wet environment, normally under a slight pressure, in an autoclave, to elevate the boiling point. As the temperature approaches 150°C, water plasticizes the molecules and the internal cracks and fissures fuse together. Silver sulfide staining (Chapter 17) can be used to examine for cracks and fissures. 

Chemical resistance (reagent resistance] n. The ability of a plastic to maintain structural and esthetic integrity when exposed to acids, alkalis, solvents, and other chemicals. ASTM tests for chemical resistance of plastics include C 581, chemical resistance of thermosetting resins used in glass-fiber-reinforced structures D 543, resistance of plastics to chemical reagents D 1239, resistance of plastic films to extraction by chemicals D 1712, resistance of plastics to sulfide staining D 21451, test... 

Sulfide staining n. (1) Discoloration of a plastic caused by the reaction of one of its constituents with a sulfide in a liquid, solid, or gas to which the plastic article has been exposed. Stabilizers based on salts of lead, cadmium, antimony, copper, or other metals sometimes react with external sulfides to form a staining metallic sulfide. (2) The formation of dark stains in a paint film, as a result of the reaction of atmospheric hydrogen sulfide with metallic compounds such as lead, mercury, or copper in the paint. 

Lead driers have traditionally been the most common, although toxicity concerns now severely restriet their use. Lead is a secondary drier as its sole function is to catalyze oxygen uptake. This and its relatively low reactivity make it a good through drier. For this reason it was widely used in combinations with primary driers in the past. It is still used where toxicity and atmospheric sulfide staining do not rule it out. Caleium soaps have been used with lead driers to improve lead solubility and low temperature drying. 

Cobalt sulfide is a quick and reliable method for outlining cells and is primarily used for visualizing the apical surface of retinal epithelia. Although this technique cannot be used in conjunction with other staining protocols (e.g., antibodies), it is useful for phenotypic characterization (Melamed and Trujillo-Cenoz 1975 Cagan and Ready 1989). For an example of cobalt-sulfide-stained pupal eye, see Figure 12.3B. 

COTIN 234 can be used where mercury containing preservatives have been omitted either due to the general toxicological picture, or for elimination of sulfide staining characteristics. 

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