Riemann's green is a green pigment ZnO.CoO, which is obtained by heating a mixture of zinc oxide and cobalt nitrate or by the reaction of cobalt nitrate with either or zinc sulphate.
a)When silver nitrate comes in contact with skin, it is reduced to white color metallic silver.In most cases, a black stain appears due to formation of finely divided silver which has black color.
The black color is due to the decomposition of the Ag+ ion into Ag, silver. Silver nitrate will slowly decompose with the silver ion reverting to elemental silver. The microscopic particles of silver are so small that they absorb light instead of reflecting it, and so appear black, instead of silver....
In the air, there's nothing holding the body of the helicopter still - so the rotor blades spin one direction, but the torque applied to spin the rotors tries to spin the body of the helicopter in the opposite direction. The little rotor on the tail helps keep the body of the helicopter pointed in the same direction.

One major difference between Americans and Japanese is their cultural norms and values. For example, Americans tend to value individualism and independence, while Japanese tend to prioritize group harmony and collectivism. This can be seen in various aspects of daily life, such as communication style, decision-making processes, and social interactions. Additionally, the two cultures have different customs and traditions, including food, clothing, and holidays.
Some specific types of clothing that Muslim women may avoid wearing in the Muslim community include tight or revealing clothing, short skirts or shorts, sleeveless or low-cut tops, and clothing made from see-through or sheer materials.