Bisbee daily review., 1920-02-15

is used for no other purpose than to run samples and is operated under the direction of a corps of chemists working in laboratories that. would do credit to some of the big schools of the country. are facts that are probably not known even to many men working in the mines.
 The samples to be assayed are orousht to the receiving floor of the mill in quantities ranking from one to 100 pounds each. The sample man en- ters in a record book notations tell. ing where each is from and for what contents they are to be run. From this point on a complete record of each sample is kept. The various samples are then put into pans simi- lar to the ordinary tin roasting pans and put into steel oven-like dryers It Is necessary that the material is thoroughly dry before it is run through the mill.
 The ore is carried through the mill entirely by gravity. The crusher on the first platform reduces the rock to sizes between one quarter and one half inch. From the first crusher it drops to a set of rolls where it is reduced to a fairly uniform product of about one-quarter inch pieces. From this the ore passes to a split" or Jones sampler, one-haf going down a shoot onto a conveyor belt and the other half through a second set of rolls. The half that goes through the second set of rolls is received in a pan by man at the bottom Of the mill. He puts it through a three times split" a device arranged to further divide the product into three equal parts.
 It will be seen that one of the DOT tions from this last split is only one sixth of the original sample. The purpose of this dividing process is 10 procure a uniform sample of the ore that is to be assayed. The half of the sample that falls on to the conveyor belt is carried to an ore bin and is eventually shipped to the smelter at Douglas with the two parts from the last split that are not used. About two cars of ore a month are shipped in this way; enough to pay for the operation of the mill.
 The sample, now a sixth of the original, is placed in a dryer again as moisture is sometimes retained in the center of larger pieces or rock before they are crushed It is then NldCcQ III i RAoACldAg which reduces it to a flour-like pow der and is the last operation as far as the mill is concerned.
 Before following the ore further some natural questions arise concern ing the mill. In the first place how is it possible 70 run sample after sample. some high grade and some low, through Q biz piece of machinery like this mill without the high grade samples hOpeiessly salting the low? Every nook and corner of the ma chinery is blown out by compressed air before each sample is run. The operators at the different stages of the mill pull lever and compressed air automatically does the rest. Even with this system a person familiar with the care that must be taken to prevent salting is inclined to be skeptical as to the possibility of cleaning the rolls and crushers of every particle of metal but c. H. Compton in charge of the assay oe- partment said that the mill had been repeatedly tested in this respect. high grade sample has been run through and then a sample contain ing no metal whatever and the latter has not been salted.
 The mill is a new type 12x12 bal anced roll with feeder. The equip- ment includes Q 6X15 roll jaw crush CT with manganese steel jaws, and a 16x1O high grade automatic balance roll with feeder, all supplied by the Sturtevant Mill company. The ma chinery is operated by two g. two 10 ! and one 20 horsepower motors.
 The pulverized sample is nov brought 10 the laboratory where 1t is "rolled". that is. it is dumped on 2 piece of cloth the corners of which are picked up alternately. thus roll | ing it about and thoroughly mixing it !! This is necessary as in the milling process some of the heavier, metallic | particles may have automatically | sifted to the bottom. The daily rec i ord sheet of the sample starts here, each laboratory department keeping records
 The sample is now taken to the | weighing room where the various sample men weigh out a part-gen- erally half a gram-that they will test. This weighing is done on fine ly balanced chemists scales in glass cases. One man weighs out a part to test for copper. another a part to test for silica and alumina, iron lime ana Sulpnur, ana IT II IS 10 De run TOT silver and gold, part will be taken for that I
 From the weighing room the sam- ples are taken to the laboratory prop CT, where the chemists make the va rious tests that will give a complete analysis. For copper the iodide meth. cd is used which will give the copper content to within five one-hundredths of one per cent. If a gold and silver assay is to be made q sample is taken to the furnace room where it is put through shelter process in minia- ture. Silica and alumna assays are made in these same furnaces which are G. Y. size, case. oil fired fur naces The final weighing on silicas, sulphers, insolubles and alumina is made in a second weighing room on ! chemists scales.