The lime charged unites with the phosphorus of the iron and takes it into the slag which covers the bath. If necessary, further additions of lime may be made from time to time during the melting and the “working down” (elimination of the metalloids) of the charge. As long as the slag is kept basic it retains the phosphorus, but should it turn acid the iron of the bath would take the phosphorus back again. These reactions are all chemical, just as much so as are the burning of wood and coal and the thousands of reactions which are brought about in chemical laboratories. Additions of ore are made from time to time and the bath rabbled. Samples are taken now and then with a long handled iron spoon or ladle and these are poured into molds to form small bars of steel, which, after quenching, are broken. [Illustration: OPEN-HEARTH FURNACE “TAPPING” ] The melter has become very proficient in judging the composition of the metal of the bath from the fracture of these broken test pieces. By means of the samples taken he watches the elimination of the metalloids. When he thinks the reactions have progressed far enough he takes a last sample which is rushed to the chemist who makes a hurried “control” analysis for carbon and phosphorus, the metal being held in the furnace meanwhile. If the results of this analysis show the bath to have the desired composition the steel is poured. If the reactions have not been complete, the chemist’s report shows that the carbon and perhaps the phosphorus are still too high, in which case the charge must be still further worked down. Some melters are able to make fairly uniform and satisfactory steel without a chemist, but for best results a chemical laboratory is desirable. When ready to tap, the big ladle is suspended from a crane under the spout of the furnace. With a tapping bar the plug of clay is removed from the tap hole and the molten steel gushes out into the ladle. The slag which has covered the bath is the last to drain out. Many times this will overflow the ladle, making a beautiful cascade as it pours over the sides all around to the floor beneath. Especially at night is this a glorious sight. [Illustration: TEEMING THE STEEL INTO INGOT MOLDS ] Recarburization is not done to the same extent as it is in the Bessemer process. As the open-hearth elimination of carbon is slower and under so much better control, the furnace usually is tapped when the carbon has been reduced to the percentage desired in the finished steel. When it is necessary to add carbon it is done sometimes by adding pig iron to the bath and sometimes by throwing a weighed amount of coal or coke in the ladle as the steel is going in. Molten iron and steel have strong appetites for carbon and dissolve it very readily. Ferro-manganese is used to prevent red-shortness and to deoxidize the metal. This also is usually put into the ladle as too much loss would occur were it added in the furnace.