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ROTTEN STONE

A mineral powderdisintegrated rock of limestone naturefound near Bake well in Derbyshire and elsewhere, containing a large proportion of alumina; highly prized for polishing purposes.

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ROSANILINES

The animated bases of fuchsine or magenta dyes. The rosanilines are colourless, crystalline compounds, and only form dyes when united with an acid. Rosaniline and pararosaniline are obtained by precipitation of their salts with alkalies. The actual dyes are the salts of these compounds, and include magenta, otherwise known as fuchsine, rosaline nitrate , rosaniline acetate , and parafuchsiue. These all dye wool and silk without a mordant, giving a magnificent fuchsinered colour in solution, but are themselves in crystalline form, of a bright metallic green lustre. They are soluble in hot water and alcohol. Rosaniline yields rosolic acid by treatment with nitrous acid. The formulae of rosaniline and pararosaniline may be shown as below:

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RESINITE

is the name of a sort of resin made by the action of formaldehyde upon phenol.

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REICHERTWOLLNY FAT VALUES

The values of the volatile fatty acids contained in fats, represented by the amount of alkali required to neutralize them, as obtained by a special process of separation and distillation.

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REAGENTS

Solutions of various chemicals used for testing purposes in qualitative analysis. They comprise strong hydrochloric, nitric, and sulphuric acids dilute solutions of the same acids and various salts containing about 5 per cent, of the respective substancesthat is to say, 5 grammes by weight per 100 c.c. dissolved in water. For use in the practice of volumetric analyses, solutions of known strength, or socalled “standard solutions,” are employed, the quantities of the constituents bearing the same relation to each other as the numbers which express their chemical equivalents. When they are made of such strengths. that a litre contains equivalent weights in grammesfor example, 365 grammes in 1,000 c.c.they are termed “normal standard solutions.”

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REDONDA PHOSPHATES

Natural phosphates of iron and aluminium found in the Islands of Redonda and Alta Vela.

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ROSOLIC ACID

A beautiful greencoloured crystalline substance with a metallic lustre and meltingpoint 270 degrees C., chemically related to aurine. It is soluble in alcohol and ether, and is used in dyestuffs.

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REFRIGERATE

To make cool. There are processes for refrigerating perishable and other articles based upon the cooling which is produced by causing volatile liquids like strong ammonia and liquefied carbon dioxide to assume the vaporous state. This change of state involves the consumption or absorption, so to speak, of heat, and is used for cooling chambers in which foods, etc., are kept. A kilogram of liquid ammonia evaporated at io degrees C. absorbs 3223 calories. With regard to the preservation of meat and fish, it has been shown that, by sufficiently rapid cooling to a temperature that corresponds to the eutectic of a saline solution, the separation of frozen water as a visible phase is avoided, so that upon thawing, the system returns to its original state. Processes of refrigeration are often used in chemical investigations and operations.

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RHATANY ROOT

The dried root ot Kramevia tviandva, containing from 8 to 20 per cent, of a tanning material.

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REVERBERATORY FURNACE

A furnace so constructed that the fuel flame in passing to the chimneyshaft is made to pass over the materials lying upon its bed these materials being the substances to undergo chemical change by action of the heat thus imposed.

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