,lug.,
IV'j
T H E J O G R N A L OF I N D U S T K I . 4 L
I
POSSIBLE STERILIZING PROPERTIES OF DENTAL CEMENTS Editor of the Journal of Industrial and Engineering Chemistry: I n THISJOVRNAL, March, 1915, appeared an article by Paul Poctschke, entitled "The Gerniicidal Eficiency of Dental Cements." The concluding paragrap11 promised reports nn the comparative strength and other properties. These reports would be, as Mr. Poetschke states, "of more immediate interest to the dental profession" and it will be by clinical experience in the hands of the dentist that this subject will receive its final analysis and probably be reported mainly in the dental literature. Since Mr. Poetschkc very pointedly refers to and criticize5 my paper cntitlcd "Possible Sterilizing properties of Filling Materials," publishcd i n thc I k a t a l Rcuiero, June, , 9 1 4 , it may he of interest " t o chemists and bacteriologists" to have reproduccd in 'Iiils JOURNAL the one illustration criticized by Mr. Poetschkc, the criticism being mostly that ouly comparative inhibition has been shown and thai there had heen no bacterial count. 111 my paper under criticism there is tlie statement: "Subjection of hardened pellets to media has been of interest, but it is by the applicntion of freshly mixed cement to inoculated agar that We closely duplicate the placing of cement into a tooth cavity." This referred to a cavity from which all infected material had not been removed, there being, for this reason, a need of a sterilieini. filline. It is well known bv the dental
profession t h a t a real copper orid cement will furnish the means o f sterilization of such an inivcted area, and yet furnish a mass, after proper setting, which is so highly insoluble that it would only show potency in the hardened state equal io the best of the so-called copper cements tested by Mr. Poetschke, including that made by tlic L. D. Caulk Company, thc employers of Mr. l'oetschkc. The qoestion of whether the testing of cements in the freshly mixed OT the hardened state has most clinical significance is bring logically considered by all interested. I n some attempts by the author, looking to an improvement of tlie integrity of dental cements, and an imparting of sterilizing properties thereto, the incorporation of precipitated copper with so-called onyphasphates o( zinc available, was one of thc means employed. In this ernploymcnt of precipitated copper, it was itlcidentally observed that the film of oxid on the surface of the particles tended to make cement when the precipitate was mixed with an acid phosphate solution. This seems to have been the first suggestion of the cement-making power of the copper onids. Before dental societies and in the dental literature as early as 1894, xttention was called to t h e cement-making property of the cuprous and cupric oxids, and the statement was then offered that the cupric furnished the better cement, all propcities considered. There has been much clinical advantage taken of the germicidal efficiency of the combination and there has naturally been a general desire t h a t a n equally efiicknt material might exist of a color not limiting its use.
.
INU ENGINEEKING CHEMISTRY
7 23
The difference in germicidal efficiency between a rea1 copper orid cement and an oxyphosphate of zinc cement, more or less modified by a copper compound, each in a freshly mixed state, is so great that results may be shown which appeal to t h e naked eye instead of needing microscopical count. For this reason in the presentation o i the paper referred to, many such results were shown. In the illustration here shown, the inoculation of the agar was ruch as would bc termed overwhelming in testing hardened pellets. With this inoculation thcrc would need to be extreme dilution to enable a count. Fig. I shows the consistent inhibition by a rral copper oxid cement. On the agar oi the Petri dish No. z was placed mixture No. I , a real copper oxid cement, No. 2, a zinc oxid cement Carrying a small percentage of orid of mercury (yellow), and No. 3, a pellet of the "wliitc copper" cement mmuiactured by Mr. I'octschke's employers. Whether this method carries proper clinical significance, is, as we have said, being logically considered by those most intimately interested. W. V-B. AMES 'CHB W. V.-B. A s s 8 COMPANY CWICACO. July 9. 1915
NOTES ON THE DETERMINATION OF HYDROCARBONS AND HYDROGEN IN GAS Editor o j lhe Journal of Industrial and Engineering Chemistry: Evcrv one who has determined the hydrocarbons in gases by combustion knows how irritating it is when the platinum spiral becomes overheated during combustion and melts, thus spoiling the analysis. If the combustion pipette eonvaina t h e e electric leads instead of two, there can be two different circuits with two different platinum spirals, so that, if one should be melie-d, i i would be merely necessary to turn the current through the other, and thus the sample can be saved. and the determimation finished. This has saved many a determination for me. When hydrogen is cletcrmined by the Palladiuinized Asbestos Method, trouble is often encountered owing to a film of liquid passing into the capillary tube, moistening the palladium and destroying its powcr of catalyzing the oxidation of hydrogen. If near rach end of the pdladium txbe a small enlargement is blown, the films of liquid will be stopped, and the palladium will not become wet. Since using the palladium tube enlarged in this way, all of my trouhles. due to the palladium becoming "poisoned," have ceased.
D. J. DEMOREST
Onr" STATE UNlVBRSiTY Cor.uMnns. April 21. 1915
NOTE ON THE DETERMINATION OF FAT IN MOLASSES FEEDING STUFFS When tnaking fat determinations on molasses feeding stuffs
