The washing is continued until the filtrate is free from salts or acids.
The liquid is filterpressed, and any excess of iron in the filtrate is precipitated by the careful addition of caustic soda and then removed.
The filtrate, which may be collected in glass vessels if an excess of hydrofluoric acid has been avoided, deposits the greater part of the salt on cooling.
The iron and aluminium precipitates are filtered off, and the filtrate boiled, when a basic beryllium hydroxide containing a little ferric oxide is precipitated.
These are washed with ammonium chloride until the filtrate is colourless, ignited, fused with caustic potash and nitre, the melt dissolved in water and nitric acid added to the solution until the colour of potassium ruthenate disappears.
Ammonium carbonate is added to the filtrate; this precipitates calcium, strontium and barium.
The filtrate, on being boiled down, yields a second crop of uranate.
If this be dissolved in water and the solution concentrated, some silicic acid separates and the filtrate deposits triclinic prisms of tungstosilicic acid.
Hot air is blown into the filtrate, which contains ferrous or calcium chlorides, to expel the excess of sulphur dioxide, and the liquid can then be used again.
The passage of the fluid is readily effected by negative pressure produced by an ordinary water exhaust-pump.The P Y Y effects of the filtrate are then tested by the methods used in pharmacology.
In the case of the tetanus and diphtheria bacilli, the production of soluble toxins can be readily demonstrated by filtering a culture in bouillon germ-free by means of a porcelain filter, and then injecting some of the filtrate into an animal.
In many cases, however, the filtrate, when injected, produces comparatively little effect, whilst toxic action is observed when the bacteria in a dead condition are used; this is the case with the organisms of tubercle, cholera, typhoid and many others.
The lead sulphate, re-precipitated in the filtrate by an excess of sulphuric acid and alcohol, is then filtered on an asbestos felt in a Gooch crucible, washed with dilute sulphuric acid and alcohol, ignited, and weighed.
The filtrate diluted to 200 cc. is carefully neutralized with hydrochloric acid, and excess of 6 cc. of the strong acid is added, and the solution saturated with hydrogen sulphide, which precipitates the copper and cadmium, metals which would otherwise interfere.
To the filtrate (or, if no silver is present, to the diluted nitric acid solution) io cc. of ammonia are added, and a standard solution of potassium cyanide is run in from a burette until the blue colour has nearly disappeared.
The solution is filtered to get rid of the precipitate, and the titration is finished in the nearly clear filtrate, which should be always about 200 cc. in volume.
It would appear to be impossible with any water that requires filtration to secure that the first filtrate shall be satisfactory if filtration begins immediately after 'a filter is charged; and if the highest results are to be obtained, either the unfiltered water must be permitted to pass extremely slowly over the surface of the sand without passing through it, or to stand upon the sand until the surface film has formed.
The pentammine purpureo-salts are formed from the luteo-salts by loss of ammonia, or from an air slowly oxidized ammoniacal cobalt salt solution, the precipitated luteosalt being filtered off and the filtrate boiled with concentrated acids.
The total alkali is determined by incinerating a weighed sample in a platinum dish, dissolving the residue in water, filtering and titrating the filtrate with standard acid.
To the filtrate from the aluminium, iron and chromium precipitate, ammonia and ammonium sulphide are added; the precipitate may contain nickel, cobalt, zinc and manganese sulphides.
To the filtrate add ammonia in excess: a white precipitate indicates bismuth; if the solution be blue, copper is present.
The colourless or amber-coloured filtrate is concentrated to 27° to 28° B., when it forms the "heavy liquor," just mentioned.
The precipitated alumina is filtered off, the filtrate evaporated and the ammonium salt of the acid purified by recrystallization.
By dissolving red lead, Pb304, in glacial acetic acid and crystallizing the filtrate, colourless monoclinic prisms of lead tetracetate, Pb(C2H302)4, are obtained.
The filtrate contains the uranium as uranous and the iron as ferrous salt.
These are filtered off hot, and the filtrate is allowed to cool, when crystals of the uranate separate out.
The filtrate is acidified with a little sulphuric acid and evaporated to crystallization.
After charging, the barrel is rotated, and when the chlorination is complete the contents are emptied on a filter of quartz or some similar material, and the filtrate led to settling tanks.
It may be obtained by heating tellurium bismuth with sodium carbonate, lixiviating the fused mass with water, filtering, and exposing the filtrate to air, when the tellurium is gradually precipitated as a grey powder (J.
In some cases the operation of filtration is performed for the sake of removing impurities from the filtrate or liquid filtered, as in the purification of water for drinking purposes; in others the aim is to recover and collect the solid matter, as when the chemist filters off a precipitate from the liquid in which it is suspended.
In filtering into a vacuum the flask receiving the filtrate should be connected to the exhaust through a second flask.
The filtrate on cooling deposits crystals of potassium zirconofluoride, K 2 ZrF 6, which are purified by crystallization from hot water.
The filtrate is evaporated to dryness (in iron or platinum vessels) and the residue fully dehydrated by gentle ignition.
The filtrate is evaporated at a temperature not exceeding 60° or at most 70° C.; after sufficient concentration it deposits on cooling anhydrous crystals of the salt, while the potassium chloride, which may be present as an impurity, remains mostly in the motherliquor; the rest is easily removed by repeated recrystallization.
The filtrate, now containing roughly two molecules of alumina to one of soda, is concentrated to the original gravity of 1.45, and employed instead of fresh caustic for the attack of more bauxite; the precipitate is then collected, washed till free from soda, dried and ignited at about looo C. to convert it into a crystalline oxide which is less hygroscopic than the former amorphous variety.
To purify the oxide, it is dissolved in dilute hydrochloric acid until the acid is neatly neutralized, the solution is cooled, filtered, and baryta water is added until a faint permanent white precipitate of hydrated barium peroxide appears; the solution is now filtered, and a concentrated solution of baryta water is added to the filtrate, when a crystalline precipitate of hydrated barium peroxide, Ba0 2 8 H 2 0, is thrown down.
The metatungstates of the alkalis are obtained by boiling normal tungstates with tungstic acid until the addition of hydrochloric acid to the filtrate gives no precipitate.
This salt is obtained by roasting wolfram with sodium carbonate, lixiviating, neutralizing the boiling filtrate with hydrochloric acid and crystallizing at ordinary temperatures.
The liquor was then filtered from the iron oxides, and the filtrate treated with scrap iron, which precipitated the copper and reformed ferrous chloride, which could be used in the first stage of the process.
Centralblatt, 1870, I, p. 340) obtained it by passing nitric oxide through a series of bottles containing tin and hydrochloric acid, to which a small quantity of platinum tetrachloride has been added; the acid liquid is poured off when the operation is completed, and sulphuretted hydrogen is passed in; the tin sulphide is filtered off and the filtrate evaporated.
A later method consists in boiling the weed with sodium carbonate; the liquid is filtered and hydrochloric acid added to the filtrate, when alginic acid is precipitated; this is also filtered off, the filtrate neutralized by caustic soda, and the whole evaporated to dryness and carbonized, the residue obtained being known as kelp substitute.