Vol. XI. No. 260. 



THE AGRICULTURAL NEWS. 



119 



METHODS OF MARKING LABORATORY 



CRUCIBLES. 



These are described in Circular No. 33, just issued, 

 of the Bureau of Chemistry of the United States 

 Department of Agriculture, and are employed for 

 marking porcelain crucibles, accounts of two methods 

 being given, one for marking with platinum and the 

 other for the application of China paints, rubber type 

 being used in both cases: — 



THE PLATINUM PROCESS. The Cfucibles are cleaned by 

 heating for half an hour with nitric acid, one part concen- 

 trated acid to one part of water. A sizing is prepared con- 

 sisting of a hot .0 per cent, solution of gelatine. The parts of 

 the crucibles to be marked are dipped into this sizing and 

 set aside to drain and dry. When the gelatine is dry, the 

 desired number is stamped on with a solution of platinic 

 chloride containing 12 to 15 per cent, of platinum — ie, 

 about 32 to 40 per cent, of the hydiated crystallized chloro- 

 platinic acid. The pad holding the solution may be made of 

 six or eight folds of smooth linen or muslin, and need not be 

 much larger than the type used. This pad is nearly saturated 

 with a few drops of the platinic-chloride solution. Too much 

 of the solution causes blurring and too little of it or too 

 dilute a solution results in dim numbers. After iLe numbers 

 are dry the crucibles are gently heated until the platinum is 

 reduced and the gelatine burned off. This is roost con- 

 veniently accomplished in a mutHe. Finally, the numbers are 

 heated for one-half minute in the Hame of the blast lamp — 

 ie , for one-half minute from the time it attains the tempera- 

 ture of the flame. 



If the wares are cleaned and fired as directed, the mark- 

 ings adhere well. The figures become more piominent if 

 burnished by use of a china painter's burnishing stone, if 

 available, or of seashore sand, or less advantageously of 

 H silica soap. The deposit is resistant to single acids, but 

 not to alkalis. In some experiments library paste was 

 substituted, with good results, for the gelatine sizing. Gold 

 and mixtures of gold and platinum solutions may be applied 

 similarl)', but there is more danger of volatalizing the gold 

 chloride before reduction takes place, and thereby causing 

 a spreading of the deposit. The resulting figures also are 

 less conspicuous than when platinum is used. This method 

 of getting the deposit of platinum or gold may possibly find 

 use also iti decorating chinaware. If the .solution is applied 

 ■with a brush, a quill, or a glass stylus, it may be more 

 dilute. The same method applied to silica wares also gives 

 very satisfactory results. 



APPLICATION OF CHINA COLOURS. Paints mixed in oil 

 are not satisfactory for use with rubber stamps because the 

 type leaves on the porcelain a rim of thickened paint while 

 the main surface of contact is relatively bare. The method 

 finally adopted is to stamp the wares to be marked with 

 a sizing or varnish similar to that which painters use for 

 applying gold leaf; 'Fat oil' — that is partly oxidized linseed 

 oil, supplied by paint dealers — proved very satisfactory for this 

 purpose. While this sizing is still sticky, the dry pigment 

 is dusted on with a camel-hair brush. After the varnish 

 has set the excess of pigment is wiped oif and the crucible is 

 fired at a strong red heat, preferably in a muffle. The fat 

 oil dries slowly. This is an advantage because then some 

 tiire may be allowed between its application and the dusting 

 on of the pigment for the irregular layer on the porcelain to 

 draw out by surface tension into a smoother one. Standing 

 overnight at room temperature, or for one hour in a drying 

 oven at 100°C , suffices for the varnish to set. The pad used 



for 'inking' the type may con.sist of .several thicknes.^es of linen 

 cloth and is nearly saturated with this varnish Too much 

 varnish on the pad must be avoided, as it results in figures 

 with ragged outlines. This varnish may readily Vie cleaned 

 from the rubber type before it has set, by the use of a lO-per 

 cent, alcoholic solution of caustic potash applied with a small 

 bristle brush. 



THE FORTHCOMING INTERNATIONAL 

 RUBBER EXHIBITION. 



The first meeting of the honorary advisory committee 

 of the International Kubber and Allied Trades' Exposition, 

 to be held in New York in September next, was held 

 recently at the London Chamber of Commerce, Oxford 

 Court, "e.C. Sir Henry A. Blake, G.C.M.G. ( President of the 

 European committee) occupied the Chair. 



The Chairman said they were meeting there for the 

 purpose of deciding what course should be taken, espec- 

 ially by the growers of plantation rubber in the Near East, 

 with regard to the great exhibition which had been arranged 

 to take place in New York, under the able management of 

 Mr. Manders. The question for the committee to consider 

 was what benefit was to be derived from this exhibition by 

 the rubber growers of the Near East and possibly by some 

 of the manufacturers in Great Britain. It seemed to him 

 that it would be to the interests of rubber growers to present 

 the plantation rubber in New York as it was presented in 

 London, because, although they did have American buyers 

 over here, the fact remained that in New York they had 

 never yet had placed before the great rubber market, which 

 took half the rubber of the world, the excellent condition of 

 the rubber production in our eastern colonies. He need 

 hardly say that if they appreciated those conditions it could 

 not but be beneficial to the owners of plantations in Ceylon 

 and Malaya. Therefore, in his opinion, it was advisable that 

 rubber growers should make as good a show as possible in 

 New York. He thought that perhaps knowledge of what 

 they were doing in the East might be of advantage in attract- 

 ing American capital and American orders. They must 

 remember that there was a stupendous market to be opened 

 in future in America for our productions, with excellent 

 remunerative prices, and thej' must look forward to the day 

 when they required all the markets of the world. 



The Organizing Manager (Mr. Manders) submitted a 

 report, in which he stated that since the commencement 

 of the organization on October 1 last year, he had been 

 meeting with most spontaneous support from rubber 

 companies and from the manufacturers and allied trades 

 of America, so that the success of a high class exhibition 

 was already assured. Mr. Manders added that Professor 

 Dunstan (Director of the Imperial Institute, London) was 

 making a magnificent exhibit of known rubbers in British 

 possessions. 



Mr. Norman W. Grieve moved that a Committee con- 

 nected with the Fiubber Growers' Association and the Malay 

 States' known agencies should be appointed, with the object 

 of securing subscriptions from home companies or individuals 

 with properties in Malaya, towards the cost of the representa- 

 tion of Malaya at the International Kubber Exhibition. 



The resolution was seconded and carried, and similar 

 resolutions were also agreed to with regard to Ceylon, Suma- 

 tra, Java and Borneo. (The India-Ruhher Journal, February 

 10, 1912.) 



