If any egg laying flock does receive an antibiotic, it is usually under the supervision of a veterinarian and only for a short period of time to treat a specific disease outbreak or for prevention of a recurring disease on that farm. What does Grade A mean? Eggs are graded based on their quality and appearance. Grade AA eggs have thick, firm whites and high, round yolks. Their shells are clean and unbroken. Grade A eggs are like Grade AA, but their whites are reasonably firm. Grade A eggs are usually sold in stores. Grade B eggs have thin whites and wider yolks. The shells are unbroken, but might show slight stains. How are eggs packed? An egg is placed in the carton with the large end up.
Arsenic has been known since ancient times, though probably in compound form rather than in its pure state. It is used in combination with other materials in pigments, poison gases and insecticides (such as Paris Green, calcium arsenate and lead arsenate) and is well known from former use as a rat poison.
Arsenic trioxide is also important as a raw material for products containing arsenic. Because arsenic is an element like carbon and oxygen it does not break down in the environment into simpler substances-though it can change form and combine with other elements into molecules that have different chemical properties.Some forms of arsenic are quite toxic; others are less so.Most arsenic compounds are undetectable to the senses, since they have no smell or taste. But when arsenic is heated-by bright sunlight or in a laboratory experiment-it passes directly from its solid state to a gas and gives off a distinctive garlic odor.ost arsenic compounds are undetectable to the senses, since they have no smell or taste. But when arsenic is heated-by bright sunlight or in a laboratory experiment-it passes directly from its solid state to a gas and gives off a distinctive garlic odor.