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636. Give different ways for the preparation of phosphine, and describe its properties. Can it be prepared by direct union of its elements, and if so, how?

637. What occurs when spontaneously inflammable phosphine is left in contact with (a) charcoal, (5) sulphur, (c) potassium permanganate solution?

638. How is phosphine obtained quite pure ? What change in volume occurs when electric sparks are passed through the pure gas?

639. Under what circumstances is phosphine spontaneously inflammable ?

How may the gas be made to lose and regain the property of inflaming spontaneously?

640. Compare the properties of phosphine with those of ammonia. What is the action of each on silver nitrate solution ? Give equations.

641. How may phosphine be combined with hydriodic acid, what is the formula of the compound produced, and how may

it be best obtained in quantity ? 642. How are the liquid and solid hydrogen phosphides prepared, and what are their properties? Give the formula for each.

643. How much oxygen, by weight and volume, is required to burn completely 179 c.c. of phosphine ?

644. Twenty-seven c.c. of phosphine are added to 39 C.c. of hydriodic acid. What occurs ? Give the weight of the solid and the volume of the gaseous product.

645. ow are the trichloride and pentachloride of phosphorus respectively obtained ? How may the trichloride be obtained from the pentachloride and vice versâ ?

646. What is the action of phosphorus trichloride on each of the following bodies? (a) water, (6) sulphur trioxide, (c) sulphuric acid, (d) alcohol, (e) sulphuretted hydrogen, (f) acetic acid. Give equations.

647. What is the action of phosphorus pentachloride on (a) water in small quantity, (6) excess of water? Give also its action on all the other substances mentioned in the previous question. Give equations.

648 What is the formula of the substance called phosphorus oxychloride ? Give various reactions for obtaining it, and state its action on water and on alcohol.

649. How are the bromide and iodide of phosphorus obtained, and what is the action of each on water ?

650. Give the formulæ of the two fluorides of phosphorus, and state how each is prepared.

651 What is the composition of the white fumes formed when a piece of dry phosphorus is exposed to air? How is the substance obtained in quantity ?

652. Name the two oxides of phosphorus, give their formulæ, and state how they are prepared. Represent by equations the action of water on each.

653. Nine grammes of phosphorus pentoxide exposed to air gained 2976 grammes. Find the percentage composition of the product so obtained.

654. How could you obtain phosphorus from phosphorous pentoxide ?

655. How much water must be added to 187 grammes of phosphoric anhydride so as to convert it into phosphoric acid ?

656. Give the names, formulæ, and percentage composition of the three acids of phosphorus.

657. What happens when phosphorus is heated with (a) solution of potash, (6) solution of barium hydrate ? Give equations.

658. How is hypophosphorous acid prepared ? What occurs when it is (a) heated, (6) added to copper sulphate solution, (c) added to silver nitrate solution ? Give equations.

659. Give the constitutional formula of hypophosphorous acid, and the formulæ of its potassium and barium salts.

660. Give two different methods for obtaining phosphorous acid, and state what occurs when it is heated. Give equations.

661. Give the volume of the gaseous product at N.T.P. which should be obtained by heating 79 grammes of phosphorous acid.

662. Write the formulæ of the sodium salts of hypophosphorous, phosphorous, and phosphoric acids.

663. Give different methods which may be used for preparing ortho-phosphoric acid.

664. What changes occur when phosphoric acid is heated (11) to 215° C., (6) to a red heat ? Give the formula of each product, and express the reactions by equations.

665. How may orthophosphoric acid be prepared from bone-ash?

666. What is meant by saying that phosphoric acid is tribasic ? Give the formulæ of the sodi:ım orthophosphates, and state how they are prepared.

667. How much phosphoric acid should be obtained by the oxidation of 1796 grammes of phosphorus with nitric acid ?

668. What is the composition of the salt obtained by adding sodium carbonate to orthophosphoric acid till the latter ceases to redden litmus-paper? What salts are obtained by adding to this one, (a) phosphoric acid, (6) caustic soda ?

669. Give the reaction of silver nitrate on each of the salts obtained by the processes mentioned in the previous question.

670. What is microcosmic salt, and how is it prepared ? What occurs when it is heated ? Give an equation.

671. When cominon sodium phosphate is heated till it ceases to lose water, what is the composition of the

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