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burned in oxygen 8.77 grammes carbon dioxide. Find the percentage of carbon contained in it.
195. How may graphite be obtained artificially?
196. Give an account of the different methods em ployed for preparing charcoal from wood. How would you demonstrate the preparation of charcoal on the small scale ?
197. Although the specific gravity of charcoal is about 1'5, yet it floats on water. How is this explained ? How could a piece of charcoal be made to sink in water ?
198. What happens when a piece of perfectly dry charcoal is placed in a jar of ammonia gas standing over mercury? What is the cause of the change?
199. How does charcoal act as a disinfectant ?
200. What happens when charcoal is heated with solution of indigo or logwood ? Which kind of charcoal acts most readily on these bodies, and to what useful purpose is it applied ?
201. What is coke? Give the different ways employed for preparing it.
202. How is animal charcoal prepared, and what are its properties?
203. How is the substance called gas carbon obtained, and what is it used for ? How is lamp-black obtained ?
204. What weight of carbon dioxide will result from burning 112 lbs. of charcoal containing 85.73 per cent. of carbon ?
205. What relation has been noticed by Angus Smith to exist with regard to the volumes and weights of gases absorbed by charcoal ?
206. Name the most abundant rninerals in which silicon occurs.
Name other substances of which it is an essential constituent.,
207. How are the different modifications of silicon prepared ? How was it originally prepared, and by whom? Give equations for all the reactions..
208. A specimen of granite contains 61 per cent. quartz, 30 per cent. potash felspar, and 9 per cent. mica. Find the percentage of silicon in the specimen.
209. Give the chief properties of amorphous and crystalline silicon, and state the action of heat, of acids, and of alkalies on each variety.
210. How much silicon should be obtained from 119 grammes of potassium silico-fluoride, and how much potassium would be needed for the decomposition ?
211. One hundred and twenty-three grammes of aluminium were heated in a current of silicon tetrachloride vapour.
Give the weights of the products.
212. How does nitrogen occur in nature ? Mention some gaseous and solid bodies which contain it.
213. When, by whom, and how was nitrogen discovered ?
214. Give a full account of any experiment which proves the existence of nitrogen in air.
215. Give two methods for the preparation of nitrogen from air.
216. Give four distinct methods for obtaining nitrogen gas from compounds of nitrogen. Give equations
217. What are the properties of nitrogen ?
218. What volume of chlorine must be passed through ammonia so as to yield 10 litres of nitrogen gas at N.T.P.?
219. What volume of air contains i gramme of nitrogen?
220. How may nitrogen be directly combined with oxygen, tungsten, carbon, boron, and magnesium ?
221. How may the nitrogen contained in potassium nitrate be obtained in the free state?
222. What is the difference in weight between 10 litres nitrogen and 10 litres air, each gas being measured at N.T.P. ?
223. What is the chief source of phosphorus and its compounds? What is the most abundant phosphate found in nature ? Name other naturally-occurring phosphates.
224. From what source do animals derive the phosphorus which is contained in their bones and blood ?
225. By whom and when was each modification of phosphorus discovered ?
226. Give the details of the process employed for the preparation of phosphorus from bone-ash. Represent all the reactions by equations.
227. In preparing phosphorus, sand is sometimes used along with charcoal for the final distillation. What is the advantage of this ? Calculate the quantity of phosphorus which should be obtained from a ton of calcium