INDUSTRIAL A N D ENGINEERING CHEMISTRY
424
of 1 per cent fudural content requires approximately 100 pounds of steam for each pound of furfural distilled, and a distillate of 5 per cent furfural content requires approximately 20 pounds of steam to accomplish the same result. Since the data show that the furfural content of the distillate becomes less as the water in the charge is increased, it is apparent that the steam requirements increase along with the liquidsolid ratio. The steam required for the digestion in experiment 634 can be readily estimated. To heat the charge and digester from room temperature to the reaction temperature will require approximately 825 pounds of steam. On a 10 per cent yield basis this is equivalent to about 1.8 pounds of steam per pound of furfural. With a distillate of 5.8 per cent furfural content, approximately 17 pounds of steam per pound of furfural will be required to distil the furfural from the reaction chamber. With ample allowances for heat losses and losses in furfural by distillation, the steam required per pound of furfural will be well below 25 pounds of steam for the digestion part of the process. This estimate has been verified from steam meter readings over long periods on a manufacturing basis. I n processes for making furfural which have used enough water or dilute acid to cover the material,6j8 or a liquid-solid ratio of 4 : l to 5:1, the steam expenditure in
Vol. 19, No. 3
the digestion part of the process has been from two to three times this amount. It is of interest to point out in this connection that the minimum steam requirements in the analytical methods, in which theoretical yields are obtained and in which the liquid-solid ratio is more than 100:1, amount t o 2500 to 3500 pounds for each pound of furfural obtained in the distillate. Within the digester occur the conversion of pentosans into furfural and the distillation of this furfural. The coordination of these two steps or stages so that the furfural is removed soon after its formation is essential to good yields. Continuous steam distillation combined with stirring, in order to mix thoroughly the steam current and the reacting materials, assist in the efficient removal of the furfural. The kind and quantity of acid, as well as the temperature employed, affect the conversion. The liquid-solid ratio used appears of lesser importance for the conversion, but does have a decided bearing on the amount of steam required for the removal of the furfural. Water equal to one-third to onefourth of the oat hulls is ample for the conversion and at the same time enables the furfural formed to be removed with the minimum of steam, and herein lies one of the chief advantages in the use of a low liquid-solid ratio for furfural manufacture.
A Guide for Cutting Paper Strips for the Gutzeit Determination of Arsenic’ By E. L. Green THESTATE COLLEGE OF WASHINGTON, PULLMAN, WASH.
I
N MAKIKG arsenic determinations by the GutzeitSanger-Black procedure2 the test paper is to be cut into strips exactly 2.5 mm. wide and approximately 12 cm. long. It has been found important that the strips be uniform in width, that the tubes into which they fit be of very nearly the same internal diameter (3.0 mm.), and that the strips fit fairly closely into them if other dimensions are chosen. The effect of variation is to alter the length and color of the stain obtained from a given quantity of arsenic. Unexpected difficulties were encountered in the attempt to provide strips accurately cut to these specifications. I n the effort to solve these recourse was had to the device described below. A print trimmer or trimming board with a knife a t least 15 cm. long will make satisfactory cuts, but the operation is tedious and not accurate if the individual widths must be laid off on the paper by hand. The accompanying figure represents a guide which makes this unnecessary. A A is the stationary knife of a trimming board represented as with the moving knife and most of the board broken away. B is a planed block of wood about 1.5 cm. thicker than the height of the board from the table top and 18 cm. long. On a line CC, a t exactly the same distance from the table top as the stationary knife, and 15 em. apart, two small wood screws are driven. Their heads are left projecting 2.5 mm. In use the guide is moved along the table top with the right hand until the screw heads touch the stationary knife. Then the paper to be cut, a strip 12 cm. wide, is moved over the trimming board with the left hand until it touches the wooden surface of the guide between the two screws. A strip of paper 2.5 mm. wide and 12 cm. long now projects over the edge of 2
Received October 15, 1926. Assoc. O5cial Agr. Chem., Methods, p. 171 (19253.
the stationary knife, and if the paper is held in this position until the right hand moves the guide a few centimeters out of the way and brings down the moving knife, this piece will be cut off. These operations can be repeated indefinitely without strain to the eyes, and the movements of the guide upon the table cause the cut strips to collect under the trimmer out of the way.
The v-idth of the strip can be easily changed by driving the screws in or out. Unless very securely fastened together, two or more sheets of paper cannot be cut with this arrangement to the desired accuracy. The accuracy of the operation is not less than 0.05 mm. and the exact width of the strips being cut is conveniently determined by counting the strips cut from a measured length of paper.
