Acetylene, the Principles of Its Generation and UseCHAPTER XIV
VALUATION AND a.n.a.lYSIS OF CARBIDE
The sale and purchase of calcium carbide in this country will, under existing conditions, usually be conducted in conformity with the set of regulations issued by the British Acetylene a.s.sociation, of which a copy, revised to date, is given below:
"REGULATIONS AS TO CARBIDE OF CALCIUM."
1. The carbide shall be guaranteed by the seller to yield, when broken to standard size, _i.e._, in lumps varying from 1 to 2-1/2 inches or larger, not less than 4.8 cubic feet per lb., at a barometric pressure of 30 inches and temperature of 60 Fahr. (15.55 Centigrade). The actual gas yield shall be deemed to be the gas yield ascertained by the a.n.a.lyst, plus 5 per cent.
"Carbide yielding less than 4.8 cubic feet in the sizes given above shall be paid for in proportion to the gas yield, _i.e._, the price to be paid shall bear the same relation to the contract price as the gas yield bears to 4.8 cubic feet per lb.
"2. The customer shall have the right to refuse to take carbide yielding in the sizes mentioned above less than 4.2 cubic foot, per lb., and it shall lie, in case of refusal and as from the date of the result, of the a.n.a.lysis being made known to either party, at the risk and expense of the seller.
"3. The carbide shall not contain higher figures of impurities than shall from time to time be fixed by the a.s.sociation.
"4. No guarantee shall be given for lots of less than 3 cwt., or for carbide crushed to smaller than the above sizes.
"5. In case of dispute as to quality, either the buyer or the seller shall have the right to have one unopened drum per ton of carbide, or part of a ton, sent for examination to one of the a.n.a.lysts appointed by the a.s.sociation, and the result of the examination shall be held to apply to the whole of the consignment to which the drum belonged.
"6. A lat.i.tude of 5 per cent, shall be allowed for a.n.a.lysis; consequently differences of 5 per cent. above or below the yields mentioned in 1 and 2 shall not be taken into consideration.
"7. Should the yield of gas be less than 4.8 cubic feet less 5 per cent., the carriage of the carbide to and from the place of a.n.a.lysis and the cost of the a.n.a.lysis shall be paid for by the seller. Should the yield be more than 4.8 cubic feet less 5 per cent., the carriage and costs of a.n.a.lysis shall be borne by the buyer, who, in addition, shall pay an increase of price for the carbide proportionate to the gas yield above 4.8 cubic feet plus 5 per cent.
"8. Carbide of 1 inch mesh and above shall not contain more than 5 per cent. of dust, such dust to be defined as carbide capable of pa.s.sing through a mesh of one-sixteenth of an inch.
"9. The seller shall not be responsible for deterioration of quality caused by railway carriage in the United Kingdom, unless he has sold including carriage to the destination indicated by the buyer.
"10. Carbide destined for export shall, in case the buyer desires to have it tested, be sampled at the port of shipment, and the guarantee shall cease after shipment.
"11. The a.n.a.lyst shall take a sample of not less than 1 lb. each from the top, centre, and bottom of the drum. The carbide shall be carefully broken up into small pieces, due care being taken to avoid exposure to the air as much as possible, carefully screened and tested for gas yield by decomposing it in water, previously thoroughly saturated by exposure to acetylene for a period of not less than 48 hours.
"12. Carbide which, when properly decomposed, yields acetylene containing from all phosphorus compounds therein more than .05 per cent. by volume of phosph.o.r.etted hydrogen, may be refused by the buyer, and any carbide found to contain more than this figure, with a lat.i.tude of .01 per cent.
for the a.n.a.lysis, shall lie at the risk and expense of the seller in the manner described in paragraph 2.
"The rules mentioned in paragraph 7 shall apply as regards the carriage and costs of a.n.a.lysis; in other words, the buyer shall pay these costs if the figure is below 0.05 per cent. plus 0.01 per cent., and the seller if the figure is above 0.05 per cent. plus 0.01 per cent.
"The sampling shall take place in the manner prescribed in paragraphs 5 and 11, and the a.n.a.lytical examination shall be effected in the manner prescribed by the a.s.sociation and obtainable upon application to the Secretary."
The following is a translation of the corresponding rules issued by the German Acetylene a.s.sociation (_Der Deutsche Acetylenverein_) in regard to business dealings in calcium carbide, as put into force on April 1, 1909:
"REGULATIONS OF THE GERMAN ACETYLENE a.s.sOCIATION FOR TRADE IN CARBIDE.
"_Price_.
"The price is to be fixed per 100 kilogrammes (= 220 lb.) net weight of carbide in packages containing about 100 kilogrammes.
"By packages containing about 100 kilogrammes are meant packages containing within 10 per cent. above or below that weight.
"The carbide shall be packed in gas- and water-tight vessels of sheet- iron of the strength indicated in the prescriptions of the carrying companies.
"The prices for other descriptions of packing must be specially stated.
"_Place of Delivery_.
"For consignment for export, the last European shipping port shall be taken as the place of delivery.
"_Quality_.
"Commercial carbide shall be of such quality that in the usual lumps of 15 to 80 mm. (about 3/5 to 3 inches) diameter it shall afford a yield of at least 300 litres at 15 C. and 760 mm. pressure of crude acetylene per kilogramme for each consignment (= 4.81 cubic feet at 60 F. and 30 inches per lb.). A margin of 2 per cent. shall be allowed for the a.n.a.lysis. Carbide which yields less than 300 litres per kilogramme, but not less than 270 litres (= 4.33 cubic feet) of crude acetylene per kilogramme (with the above-stated 2 per cent. margin for a.n.a.lysis) must be accepted by the buyer. The latter, however, is ent.i.tled to make a proportionate deduction from the price and also to deduct the increased freight charges to the destination or, if the latter is not settled at the time when the transaction is completed, to the place of delivery.
Carbide which yields less than 270 litres of crude acetylene per kilogramme need not be accepted.
"Carbide must not contain more than 5 per cent. of dust. By dust is to be understood all which pa.s.ses through a screen of 1 mm. (0.04 inch) square, clear size of holes.
"Small carbide of from 4 to 15 mm. (= 1/6 to 3/5 inch) in size (and intermediate sizes) must yield on the average for each delivery at least 270 litres at 15 C. and 760 mm. pressure of crude acetylene per kilogramme (= 4.33 cubic feet at 60 F. and 30 inches per lb.) A margin of 2 per cent. shall be allowed for the a.n.a.lysis. Small carbide of from 4 to 15 mm. in size (and intermediate sizes) which yields less than 270 litres but not less than 250 litres (= 4.01 cubic feet per lb.) of crude acetylene per kilogramme (with the above-stated 2 per cent. margin for a.n.a.lysis) must be accepted by the buyer. The latter, however, is ent.i.tled to make a proportionate deduction from the price and also to deduct the increased freight charges to the destination or, if the latter is not settled at the time when the transaction is completed, to the place of delivery. Small carbide of from 4 to 15 mm. in size (and intermediate sizes) which yields less than 250 litres per kilogramme need not be accepted.
"Carbide shall only be considered fit for delivery if the proportion of phosph.o.r.etted hydrogen in the crude acetylene does not amount to more than 0.04 volume per cent. A margin of 0.01 volume per cent. shall be allowed for the a.n.a.lysis for phosph.o.r.etted hydrogen. The whole of the phosphorus compounds contained in the gas are to be calculated as phosph.o.r.etted hydrogen.
"_Period for Complaints._
"An interval of four weeks from delivery shall be allowed for complaints for consignments of 5000 kilogrammes (= 5 tons) and over, and an interval of two weeks for smaller consignments. A complaint shall refer only to a quant.i.ty of carbide remaining at the time of taking the sample.
"_Determination of Quality._
"1. In case the parties do not agree that the consignee is to send to the a.n.a.lyst for the determination of the quality one unopened and undamaged drum when the consignment is less than 5000 kilogrammes, and two such drums when it is over 5000 kilogrammes, a sample for the purpose of testing the quality is to be taken in the following manner:
"A sample having a total weight of at least 2 kilogrammes (= 4.4 lb.) is to be taken. If the delivery to be tested does not comprise more than ten drums, the sample is to be taken from an unopened and undamaged drum selected at random. With deliveries of more than ten drums, the sample is to be drawn from not fewer than 10 per cent, of the lot, and from each of the unopened and undamaged drums drawn for the purpose not less than 1 kilogramme (= 2.2 lb.) is to be taken.
"The sampling is to be carried out by a trustworthy person appointed by the two parties, or by one of the experts regularly recognised by the German Acetylene a.s.sociation, thus: Each selected drum, before opening, is to be turned over twice (to got rid of any local acc.u.mulation of dust) and the requisite quant.i.ty is to be withdrawn with a shovel (not with the hand) from any part of it. These samples are immediately shot into one or more vessels which are closed air- and water-tight. The lid is secured by a seal. No other description of package, such as cardboard cases, boxes, &c., is permissible.
"If there is disagreement as to the choice of a trustworthy person, each of the two parties is to take the required quant.i.ty, as specified above.
"2. The yield of gas and the proportion of phosph.o.r.etted hydrogen contained in it are to be determined by the methods prescribed by the German Acetylene a.s.sociation. If there are different a.n.a.lyses giving non- concordant results, an a.n.a.lysis is to be made by the German Acetylene a.s.sociation, which shall be accepted as final and binding.
"In cases, however, where the first a.n.a.lysis has been made in the Laboratory of the German Acetylene a.s.sociation and arbitration is required, the decisive a.n.a.lysis shall be made by the Austrian Acetylene a.s.sociation. If one of the parties prevents the arbitrator's a.n.a.lysis being carried out, the a.n.a.lysis of the other party shall be absolutely binding on him.
"3. The whole of the cost of sampling and a.n.a.lysis is to be borne by the party in the wrong."
The corresponding regulations issued by the Austrian Acetylene a.s.sociation (_Der Oesterreichische Acetylenverein_) are almost identical with those of the German a.s.sociation. They contain, however, provisions that the price is to include packing, that the carbide must not be delivered in lumps larger than the fist, that the sample may be sealed in a gla.s.s vessel with well-ground gla.s.s stopper, that the sample is to be transmitted to the testing laboratory with particulars of the size of the lots and the number of drums drawn for sampling, and that the whole of it is to be gasified in lots of upwards of 1 kilogramme (= 2.2 lb.) apiece.
In Italy, it is enacted by the Board of Agriculture, Commerce and Industry that by calcium carbide is to be understood for legal purposes also any other carbide, or carbide-containing mixture, which evolves acetylene by interaction with water. Also that only calcium carbide, which on admixture with water yields acetylene containing less than 1 per cent. of its volume of sulphuretted hydrogen and phosph.o.r.etted hydrogen taken together, may be put on the market.
It is evident from the regulations quoted that the determination of the volume of gas which a particular sample of calcium carbide is capable of yielding, when a given weight of it is decomposed under the most favourable conditions, is a matter of the utmost practical importance to all interested in the trafficking of carbide, _i.e._, to the makers, vendors, brokers, and purchasers of that material, as well as to all makers and users of acetylene generating plant. The regulations of the British a.s.sociation do not, however, give details of the method which the a.n.a.lyst should pursue in determining the yield of acetylene; and while this may to a certain extent be advantageously left to the discretion of the competent a.n.a.lyst, it is desirable that the results of the experience already won by those who have had special opportunities for practising this branch of a.n.a.lytical work should be embodied in a set of directions for the a.n.a.lysis of carbide, which may be followed in all ordinary a.n.a.lyses of that material. By the adoption of such a set of directions as a provisional standard method, disputes as to the quant.i.ty of carbide will be avoided, while it will still be open to the competent a.n.a.lyst to modify the method of procedure to meet the requirements of special cases.
It would certainly be unadvisable in the present state of our a.n.a.lytical methods to accept any hard and fast of rules for a.n.a.lysis for determining the quality of carbide, but it is nevertheless well to have the best of existing methods codified for the guidance of a.n.a.lysts. The substance of the directions issued by the German a.s.sociation (_Der Deutsche Acetylenverein_) is reproduced below.