1026 IRON 



in until tho instrument is filled to 0. The palm of tho hand is then securely placed 

 on the top, and the contents agitated by repeatedly inverting the instrument until tho 

 salt is dissolved and the solution rendered of uniform density throughout. Eac-h divi- 

 sion of the solution thus prepared contains 0-444 grain of bichromate, which Dr. 

 Penny ascertained to correspond to half a grain of metallic iron. The bichromate 

 must be pure, and should be thoroughly dried by being heated to incipient fusion. 

 100 grains of the pulverised iron-stone are now introduced into a Florence flask with 

 1^ oz. by measure of strong hydrochloric acid and oz. of distilled water. Jit at, is 

 cautiously applied and the mixture occasionally agitated until the effervescence 

 caused by the escape of carbonic acid ceases, the heat is then increased, and tho mix- 

 ture made to boil, and kept at moderate ebullition for ten minutes or a quarter of an 

 hour. About 6 oz. of water are next added and mixed with the contents of the flask, 

 and the whole filtered into an evaporating basin. The flask is rinsed several times 

 with water, to remove all adhering solution, and the residue on the filter is well washed. 

 (Several small portions of a weak solution of red prussiate of potash (containing 1 

 part of salt to 40 water) are now dropped upon a white porcelain slab, which is 

 conveniently placed for testing tho solution in the basin during the next operation. 

 The prepared solution of bichromate of potash in the burette is then added very 

 cautiously to the solution of iron, which must be repeatedly stirred, and as soon as it 

 assumes a dark greenish shade it should be occasionally tested with the red prussiato 

 of potash. This may be easily done by taking out a small quantity on the end of a 

 glass rod, and mixing it with a drop of the solution on the porcelain slab. When it is 

 noticed that the last drop communicates a distinct blue tinge, the operation is termi- 

 nated ; the burette is allowed to drain for a few minutes, and the number of divisions 

 of the test-liquor consumed read off. This number multiplied by 2 gives the amount 

 of iron per cent. The necessary calculation for ascertaining the corresponding quantity 

 of protoxide is obvious. If the specimen should contain iron in the form of peroxide, 

 the hydrochloric solution is deoxidised as before by sulphite of ammonia. The pre- 

 sence of peroxide of iron in an ore is easily detected by dissolving 30 or 40 grains in 

 hydrochloric acid, diluting with water, and testing a portion of the solution with sul- 

 phocyanide of potassium. If a decided blood-red colour is produced, peroxide of iron 

 is present. If it be desired to ascertain the relative proportions of peroxide and 

 protoxide of iron in an ore, two operations must be performed : one on a quantity of 

 the ore that has been dissolved in hydrochloric acid in a stout stoppered bottle ; and 

 another on a second quantity that has been dissolved as usual, and then deoxidised by 

 sulphite of ammonia or by metallic zinc. It is advisable to employ the solution of 

 bichromate much weaker than proposed by Dr. Penny, and to employ a burette 

 -graduated to cubic millimeters. A good strength is 1 grain of metallic iron = 10 

 cubic centimeters of bichromate-solution. 



Metals precipitable by sulphuretted hydrogen from the hydrochloric solution. A 

 weighed portion of the ore, varying from 200 to 2,000 grains, is digested for a con- 

 siderable time in hydrochloric acid : the solution is filtered off; the iron in tho filtrate 

 reduced when necessary by sulphite of ammonia, and a current of sulphuretted hydro- 

 gen passed through it. A small quantity of sulphur which is always suspended is 

 collected on a filter and thoroughly washed ; it is then incinerated at as low a tempe- 

 rature as possible. The residue (if any) is mixed with carbonate of soda, and heated 

 upon charcoal before the blowpipe : any globules of metal that may be obtained are 

 dissolved and tested. 



Analysis of Pig-iron. The most important constituents to be determined are carbon 

 (combined and uncombined), silicon, sulphur, phosphorus ; those of less consequence, 

 or of more rare occurrence, are manganese, arsenic, copper, zinc, chromium, titanium, 

 cobalt, nickel, tin, aluminium, calcium, magnesium, and tho metals of the alkalis. 



1. Determination of the total amount of carbon. About 100 grains of tho iron in 

 small pieces are digested, at a moderate temperature, in 6-oz. measure of a solution 

 formed by dissolving 6 oz. of crystallised sulphate of copper, and 4 oz. of common 

 salt in 20 oz. of water and 2 oz. of concentrated hydrochloric acid. The action is 

 allowed to proceed until all, or nearly all tho iron is dissolved. Carbon and copper 

 are left insoluble ; these are collected on a filter, and washed first with dilute hydro- 

 chloric acid (to prevent the precipitation of stibchloride of copper), then with vat IT, 

 then with dilute caustic potash, and finally with boiling water. The mixed carl><>n 

 and copper are dried on the filter, from which they are easily removed by a knife- 

 blade, and are mixed with oxido of copper, and burned in a combustion tube in tho 

 usual way, with a current of air, or, still better, of oxygen. The carbonic acid is 

 collected in Liebig's apparatus, from which tho amount of carbon is calculated. 



2. Graphite, or uncombined carbon. A weighed portion of the finely-divided iron 

 (filings or borings may be used) is digested with moderately strong hydrochloric acid, 

 the combined carbon is evolved with combination with hydrogen, while tho ^raphito 

 is loft undissolved. It is collected ou a filter, washed, and then boiled with a solu- 



