MR. HERAPATH ANALYSIS OF SUGAR FECULENCIES 367 XXXL-On a Cement for stopping the cavities of Teeth. BY T.J. HERAPATH, F.C.S. A good cement for stopping the cavities of carious teeth has long been a great desideratum to dentists because unfortunately almost all those now known possess some disadvantage or other. Even the copper-amalgam hitherto the one most preferred by the members of this profession and of which the analysis and mode of preparation have been recently described by M. Pettenkofer,* is apt to communicate a very unpleasant metallic taste to the food find soon becomes discoloured in consequence of the formation of a thin film of black sulphuret of copper. But in the course of the last few months another succedaneum the invention of an American gentleman has been brought into notice; and this would appear to * Ann.Ch. Pharm. June 1849. MR. HERAPATH ON A CEMENT possess every requisite that could be desired. The substance referred to is an alloy of tin and cadmium. 'When combined with a small quantity of mercury it becomes soft and semi-fluid and may then be easily pressed into the cavity of the decayed tooth where it soon solidifies into a hard tenacious crystalline amalgam thus preventing the access of air to the interior of the tooth and rendering the organ fit for the purposes of mastication. Being at the same time of a dull white colour similar in appearance to frosted silver and not liable to become tarnished close scrutiny is required in order to detect its presence.The great advantage of this latter property need not be pointed out. When about to be employed the alloy in fine powder is mixed up by the operator in the palm of his hand with from two and a half to three times its weight of mercury or such a quantity as will suffice to render it perfectly soft when it is immediately pressed into the cavity in the enamel the latter having been previously cleansed and dried by the ordinary method. The alloy above-described as may be naturally supposed is readily acted upon by acids even by the diluted vegetable acids which gradually dissolve out the cadmiurn. But as the salts of cadmiumdo not appear to produce any injurious action upon the system unless taken in large quantity of course no ill effects need be expected to result from this circumstance.This metallic combination of tin and cadmium presents us with another interesting example of the effects of crystallization and amorphism on the physical properties of bodies. As in the case of the copper-amalgam before adverted to the specific gravity does not appear to vary 111 the transition from the amorphous to the crystal- lized condition as the amalgam when hard occupies very nearly if not exactly the same space that it does when soft and fluid. In conclusion I may observe it has been found that the pro-portion of the cadmium may be considerably reduced without altering the physical properties of the compound. A mixture of 5 parts of cadmium and 7 to 8 of tin is the best and has been found to answer remarkably well.A quantity of the cement in qiiestion was placed in my hands some time since by a friend who wished to learn the nature of its com-ponents. Upon subjecting it to analysis it was found to consist of tin and cadmium in the following proportions 8.90 grs. gave 3.962grs. of Sn02and 6.629 grs. of CdO. 10800 , , 4.460 , of Sn02 , 7.429 , of CdO. 10*00 , , 4.630 , of Sn02 , 7422 , of CdO. FOR STOPPING DECAYED TEETH. It would therefore appear to be coinposed of I. 11. Irr. Mean. Tin . . . 34.899 34-960 34.980 34.946 Cadmium . 65.061 65.010 64.950 65.007 and must therefore be considered as an alloy of these two metals in the proportion of one atom of the former to two of the latter. The best mode of preparing it I find to be as follows :-Melt a quantity of bees’-wax in a pipkin over the fire and then throw in the cadmium; by these means the loss of cadmium which would other- wise result from oxidation is avoided.So soon as the metal is completely fused add the tin in small pieces till a perfectly homo- geneous alloy is formed. This can be afterwards granulated in the usual manner or by introducing it into a wooden or iron box and shaking it up rapidly while it still remains in the fluid state. Since the above was written I have analysed another and some-what similar cement which was stated by theinventor to be composed of platinum and tin. A quantitative examination however proved it to possess the following composition in 100 parts Silver . . 73.188 Tin . . . 21-127 Zinc . slight traces Platinum with very slight traces of gold . 5.685 100*000