AIDS F O R THE ANALYST were ground to minus 100-mesh by the high alumina ceramic buckboard and muller, by the conventional steel buckboard and muller, and in the agate martas. The ground samples were then analyzed spectrographically according t o the method described by Fleischer and coworkers (9). The, d+ta are presented in Table I. The sensitivity of the method 18 given in Table 11. The agate mortar and pestle is generally considered 8. satisfactory grinding medium. When the trace constituents found in a sample t h a t WBB ground in an agate mortar are compared with those found in samples ground on ceramic and steel buckboards, an appraiml can be made of t h e last two grinding materials. From Table I, column 4, i t may he seen t h a t only 0.003% magnesium is added t o t h e qurtrtBite from the ceramic muller. It is amartrent by commrina columns 5 and 10 t h a t the
A New Ceramic Buckboard and Muller Homld Bloom' and P. R. Bornelf, U. 5. Geologicol Survey. Denver Federal Center, Denver, Colo.
to pulverize rock or soil without introducing into 1.it difficult some contamination from grinding equipment. When T IS
minor constituents of a sample are being studied, this contamination must be kept t o a minimum or appreciable errors may result. The steel buckboard and muller permits rapid grinding and easy cleaning and is comparatively inexpensive. Its chief m,eakness is that when samples of extreme hardness and abrasive properties are ground on the steel, varying amounts of foreign metals are added to the sample. These Contaminants may vary when different buckboards are used because of the variable composition of the scrap iron used in making them. Ahrens ( 1 ) and Sandell ( 6 ) discuss the contaminztition that steel and iron mortars introduce in grinding. Myers and Barnett ( 4 ) identify iron, cobalt, chromium, copper, molybdenum, manganese, nickel, and vanadium a6 contaminants when B quartzite sample is ground hy the steel plates of a vertical Braun-type pulverizer. A new rugged material, tentatively called high alumina ceramic, has recently become commercially available. This material was ohtilined from the Coors Porcelain Co., Golden, Colo., and i t is probable that high alumina ceramic products of other manufactures would be equally satisfactory. Barnett, Huleatt, Rader, and Myers ( d ) have successfully used this ceramic as grinding plates in a vertical Braun-type pulverizer.
.,. .~~. " ~ ~ ~ ~ cally. On the other hand, the steel buckboard and &uller%&d sufficient contamination by iron, manganese, chromium, copper, nickel, and vanadium t o make its use objectionable in determining traces of these elements. ~~
~
~
~
CONCLUSIONS
The speed of grinding with the ceramic buckboard was about the 8ame as with the steel buckboard and muller and faster than in the agate mortar. With the buckboards it took ahout 15 minutes to reduce 30 grams of the '/&-inch fraction to minus 100mesh.
An experimental buckboard and muller has been made from this material for the U. 5. Geological Survey. This buckboard measures 12 inches by 12 inches by It/%inches and weighs about. 25 pounds. The muller is fitted with a 24inch wooden handle and weighs about 10 pounds (Figure 1). Grinding tests were made with this new equipment, with the steel buckboard and muller, and with an agate mortar and pestle t o compare: the speed of grinding, ease of cleaning, and kind and quantity of contamination. Chips of qumtaite and massive quartz were reduced t o less than >/,-inch size by heating to 600' C. and quenching in cold distilled water, followed by further shattering in a Plattner mortar. (The U. s. Geological Survey does n+ usually heat rock samples t o 600" C. and then quench them m distilled water because this procedure would invalidate later chemical analysis for ferrous oxide and water.) Separate portions of these materials
__
1 Present address, Chemistry Department, Colorado Sohool of Mines, Golden, Colo.
Figure 1
___ Table I.
Element
Fe Ti
M" CS
zf
Ground with agate (1) ..
1.0 0.04 0.0006
0.04 0.007 0.04
Q u a n t i t a t i v e Spectrographic Analyses Showing- C o n t a m i n a n t s Introduced into Samples Quartzite, % Buckboard and Muller ContaminaGround with Ground tion &l"mi+a with from cerami~ Steel ceramic(2) (3) (41 . . 1.0 1.4 0 0.04 0.04 0 0 0,0006 0.006 0 0.04 0.04 0.006 o.ooa 0.01 0.04 0.04 0
Contaminstion from steelb (51 0.4 0
0.0054 0
-0.001
0
Looked forbutnotfound: P , Ag, As. Au, B, Be. Bi, Ce, Cd. DY.ET,Ga, Gd. Ge , Hf Sm, So. Ts,Te,Th,TI,U, W , Zn. c Column (7) minus column ( 6 ) . Column (21 minus column (1). d Column (81 minus column (61. &Column (31 minus column (11.
Maisive Quartz.. % Buckboard and Muller Ground contamina- contaminaGround tion tion Ground with %l"ml?Z with iron from with steel' oeramic~ steeld oersm,c agate (01 (101 (81 (6) (71 2.4 0 0 2.4 0 0.0048 0.0001 0.0003 0.005 0.0002 0.03 0 0 0.03 0 0.02 0 0 0.02 0 0.002 0.003 0.003 0.002
